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Extend blockMesh with smoothing capability

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Old   April 3, 2014, 10:58
Default Extend blockMesh with smoothing capability
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NathanaŽl Geng
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Hello,

For some time I have been working on writing an add-on in blockMesh in order to smooth the mesh.
After compilation of the code located at Github link you simply need to add the following in your blockMeshDict:
Code:
smoother
{    
    elemTransformParameter    0.666;
    maxGETMeIter                1000;
    improvementTolerance        1e-4;
    qMeanRelaxationTable        (1 0.25 0.125 0);
    qMinRelaxationTable         (0.1 0.05 0.01 0);
    maxIneffectiveIteration     5;
    
    features
    {
        featureAngle            30;
        minEdgeForFeature       10;
    }
};
Example and explaination are availlable at link to explaination.




I encourage people to suggests improvements and make own versions.

NathanaŽl
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Last edited by nathanael; April 4, 2014 at 09:39.
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Old   April 6, 2014, 03:48
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I updated the installation instructions :
Code:
# If needed source your Open FOAM bashrc
source OpenFOAM/OpenFOAM-2.2.x/etc/bashrc

# Download the extBlockMesh source and move inside downloaded directory
git clone https://github.com/Etudes-NG/extBlockMesh
cd extBlockMesh

# Copy patch in OpenFOAM source and patch it
cp OF-extBlockMesh-2.x.x.patch $WM_PROJECT_DIR
cd $WM_PROJECT_DIR
patch -p1 < OF-extBlockMesh-2.x.x.patch

# Go back in the directory where you download the extBlockMesh source
cd extBlockMesh

# Run the installation script
./Allwmake.sh

# Run extBlockMesh in place of blockMesh
Hope this will help.
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Last edited by nathanael; April 10, 2014 at 11:51. Reason: Correct installation instructions
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Old   July 27, 2014, 09:05
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Fumiya Nozaki
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Hi nathanael,

Thank you for sharing the useful tool and pointing out the GETMe smoothing approach.
I'm learning this method from your code and I have one question.

According to the paper(http://cames.ippt.gov.pl/pdf/CAMES_20_1_4.pdf),
the new mesh node positions are calculated using the formula (9).
I think the weighting coefficients are calculated differently in your code.

Could you look at the attached file and answer my question?

Best regards,
Fumiya
Attached Images
File Type: png Question_GETMe1.PNG (31.2 KB, 234 views)
File Type: png Question_GETMe2.PNG (8.8 KB, 120 views)
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Old   August 3, 2014, 12:26
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NathanaŽl Geng
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Hi Fumiya

From the same document on page 59 I read:
<Here N_j denotes the index set of the neighbor elements of E_j, i.e., elements, which share at least one node with E_j>
I understand all red cells in your picture.

There is one error in this part of the code, I correct it for the next release, but unfortunately my hard drive crash and I lost all the git history for this project... So I cannot give you the exact location. (Missing divides by the number of cells somewhere).

The next release is ready for public release in a few weeks.
This release gives a lot of improving in term of speed and some extra stuff... I would not say that blockMeshDict become easy to make but at least less to do with complex edges

Best regards,

NathanaŽl.
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Old   August 3, 2014, 12:52
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Oups I was to fast... Yes you are true: I need to compute the weight for the cell and not the point. I will correct that.
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Old   August 4, 2014, 04:29
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Hello Fumiya,

Here is a comparison between the two algo, colored using skew quality from paraview (lower is better):



For me this is better with old code (avg quality = 0.8904 vs 0.8896, min quality = 0.7429 vs 0.7201).
And a bit faster with old code, no need to store or compute the list of neighboring cells.

What is your opinion? Have you done some test on your side?

Best regards,

NathanaŽl.

Last edited by nathanael; August 7, 2014 at 03:28.
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Old   August 7, 2014, 04:27
Default Thank you
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Gerhard Holzinger
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Hi,

I installed and tested extBlockMesh. Attached you see a simple mesh of a pipe, nothing fancy. I played around with block and vertex arrangement to create a nice mesh. However, without modifying individual cells, you always reach some limit in terms of mesh beauty.

Attached are some pics and the output of checkMesh.

Great tool.
Attached Images
File Type: jpg pipeBlockMesh.jpg (85.0 KB, 317 views)
File Type: jpg pipeExtBlockMesh.jpg (76.3 KB, 312 views)
Attached Files
File Type: txt checkAllBlockMesh.txt (3.3 KB, 52 views)
File Type: txt checkAllExtBlockMesh.txt (3.4 KB, 51 views)
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Old   August 7, 2014, 04:51
Default Smoothing operation
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What I understand up to this point, is this is an enhanced version of blockMesh.
Is there a possibility to call the smoothing seperately?

In some cases I do some mesh-magic after blockMesh has finished, e.g. combine mesh regions, partial refinement.
So, I am wondering if it is possible to do the smoothing after this stuff I just descibed.
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Old   August 18, 2014, 10:47
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Hi nathanael,

Thank you for your test!

I'm considering using your code for mesh morphing operations.
The displacements of the points on the boundaries are prescribed
and the new positions of the interior points are calculated using GETMe algorithm.

Do you think this is a reasonable approach?

Best regards,
Fumiya
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Old   August 19, 2014, 07:01
Smile extBlockMesh release v0.2
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NathanaŽl Geng
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Hi all,

I'm pleased to announce the new release for extBlockMesh!

Major's change:
  • Snapping capability.
  • Run faster.
  • Construct from polymesh, easy to connect with other app.
    Code:
    MeshSmoother meshSmoother(&mesh, &smootherDict);
    meshSmoother.update();
  • hexMeshSmoother app added for smoothing of existing mesh.
  • Both hexMeshSmoother and extBlockMesh look in system folder for the dictionary "smootherDict" which contain all settings. For explanation about this dictionary see link to explanations.
  • No change in OpenFOAM code needed.



Best regards,

NathanaŽl.
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Last edited by nathanael; August 30, 2014 at 12:14.
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Old   August 30, 2014, 12:13
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Just to show some of the possibilities with a complex block topology:

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Old   February 10, 2015, 20:14
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Dear all

First of all, great thanks to Nathanael for this useful tool.
I tested the tutorial attached with the latest git ver. of extBlcokMesh, but in difficulty for my own simple test case of the 2-D O-mesh of NACA4 wing section attached.

It seemed to be OK after blockMesh command (checked by checkMesh command and Paraview), the mesh has only 20000 cells.
After that I ran extBlockMesh command but no response returns even after 1 night.
What's wrong with my mesh (blockMeshDict or smootherDict).
Any comments and suggestions are highly appreciated.



Best regards,
waku2005
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File Type: gz NACA4_Omesh.tar.gz (5.4 KB, 41 views)
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Old   February 12, 2015, 04:23
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NathanaŽl Geng
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Hello Waku2005,

The problem is located in your blockMeshDict, just comment the boundary blade. I don't understand the reason...
After your mesh is smoothed, just change the name of defaultFaces to blade in the file constant/polyMesh/boundary.

Note: your mesh is very stiff for the smoother, I recommand to reduce the transformParameter to 0.02 or less.

Best regards,

NathanaŽl.
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Old   February 12, 2015, 05:20
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Quote:
Originally Posted by nathanael View Post
Hello Waku2005,

The problem is located in your blockMeshDict, just comment the boundary blade. I don't understand the reason...
After your mesh is smoothed, just change the name of defaultFaces to blade in the file constant/polyMesh/boundary.

Note: your mesh is very stiff for the smoother, I recommand to reduce the transformParameter to 0.02 or less.

Best regards,

NathanaŽl.
Dear NathanaŽl

Thanks to your suggestion! It works well after I changed the boundary name and reduced the transformParameter to 0.02.

I also found that the convertToMeters parameter in the blockMeshDict affects the smoothing iteration,
i.e., without two changes suggested in your reply, smoothing iteration had successfully continued after I changed the convertToMeters of 1.0 to 0.1 with no change in smootherDict.
I don't know why it works even only the mesh scale was changed.

Best regards,
waku2005
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Old   February 17, 2015, 03:08
Default Gridpro topology to blockMeshDict
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Hi,

This looks like a promising tool.

I know of the gridpro2Foam mesh converter but does anyone know if a utility exists that can convert a GridPro topology (*.fra files) to a blockMeshDict file?
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Old   April 20, 2015, 10:19
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Update: problem solved!

I am trying to use extBlockMesh but I getting the following errors;

when I tried to compile it using OpenFoam 2.2.x, I got an error

SmootherBoundary.h:32:30: fatal error: extendedEdgeMesh.H: No such file or directory
#include "extendedEdgeMesh.H"

Then I tried OpenFoam 2.3.x, I managed to compile it without errors and run the tutorial as well. But, when I checked the points and faces files, I found very strange characters like binary files and I could not view the mesh in paraview.


the beginning of points file
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      binary;
    class       vectorField;
    location    "constant/polyMesh";
    object      points;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //


61776
(l/��a@���Pم*��YJH�;f@W�&�
<f@��n$��� 'A,f@i�'�La@[���0��A���Hf@1Y�^L[a@p�l��V���V�Vf@K8^L\�Za@�9�'�w@�$@�cf@�����Ka@P��ٻ�@}ҫpf@nx�0a@�	�� v$@��Q��,f@�!p\a@P� F��*@�
,�P���f@��7�.L`@7�՞G$�'�����f@�S��R`@u�e�������}��f@Wʼ3�U`@™����NL-2d�f@����U`@tō���?e�L�p�f@4,?��Q`@�����@�3����f@��!��K`@64�$@K;�B�f@`7�H`@��|6�^,@E%�[D�f@���X�_@�^,��Y/ldg@�o
��g@�8�]@^�:�wV@More��Ó�g@J-I�|�]@��%d�@�����g@��2ab�]@��Cn$@V����g@z<�A�^@Q$Pօ*@�$���g@�6���ea@�@LJ�*������f@�IL�o�a@X��h�$�Nܙ���f@FQ[C��a@�,	:W��Uڲ��f@:�ʆ��a@�k����8�lܕf

Last edited by hk318i; April 22, 2015 at 09:10. Reason: problem solved
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Old   July 23, 2015, 13:07
Default Someone knows what is wrong?
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Lorenzo Bartolucci
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Hi all,
I have just started to use extBlockMesh and I was trying to build a simpleMesh but it seems that I have done some mistakes at some point. Someone knows what is happened?
Thanks in advance,
Lorenzo
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Old   August 20, 2015, 16:28
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Quote:
Originally Posted by GerhardHolzinger View Post
Hi,

I installed and tested extBlockMesh. Attached you see a simple mesh of a pipe, nothing fancy. I played around with block and vertex arrangement to create a nice mesh. However, without modifying individual cells, you always reach some limit in terms of mesh beauty.

Attached are some pics and the output of checkMesh.

Great tool.
This looks awesome! I really want to use this add-on to improve my mesh but in what version of openfoam does it work? I tried compiling in foam-extend-3.1 and some libraries were missing.
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Old   August 20, 2015, 16:31
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I tried it before, it works with OpenFOAM-2.3
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Old   August 22, 2015, 12:16
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Quote:
Originally Posted by hk318i View Post
I tried it before, it works with OpenFOAM-2.3
Thank you Hassan! I was able to compile in foam2.3
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