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Old   March 27, 2013, 10:47
Default sHM, 2D, foils, sharp edge
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Hi all!

I had some problems with my airfoil 2D mesh.

First one was in bl at the tip of the foil. The layers just collapsed without connection.
2.jpg
I just reduced the number of surface smooth normals and this problem was solved.

Another one was in layers at the tail
3.jpg
I did not succeed. May be there is no way to solve this problem (maxConcave was 180 and featureAngle 90).

May be somebody would say something about it or suggest any idea about sHM and geometry with sharp edges?
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Old   April 2, 2013, 10:38
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I don't know if this is applicable to your case (especially since it seems that you have a very sharp TE), but you could try my 2D airfoil mesher which generates a blockMesh file ready for OpenFOAM.

http://hvirvel.dk/airfoilmesher/

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Old   April 3, 2013, 02:27
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Quote:
Originally Posted by MadsR View Post
I don't know if this is applicable to your case (especially since it seems that you have a very sharp TE), but you could try my 2D airfoil mesher which generates a blockMesh file ready for OpenFOAM.

http://hvirvel.dk/airfoilmesher/

/Mads
Thanks a lot!

I tried this mesher (is it your?) several times, but i had problems using it. May be i was due to airfoil profile data.

So for my case i developed blockMesh, with C-mesh suitable well to my test case. But sHM is just for my interest. May be little bit later i will find a solution.
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Old   April 3, 2013, 04:40
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Yeah it is mine, trouble is if you have sharp trailing edge. My generator creates o-meshes and expect some bluntness at the TE. If you just click "submit" without submitting any airfoil-data-file, it will default to a mesh for a blunt-TE NACA0015. There is an example airfoil-data-file on the page too.

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Old   April 3, 2013, 04:52
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If you want to try I have made a C-mesh generator here: https://www.hpc.ntnu.no/display/hpc/...l+Calculations (see bottom of page). It can work with sharp trailing edges. Currently it generates NACA 4-digit airfoil meshes, but as long as you can get a table of coordinates into the script, it will mesh any airfoil with some small modifications.

However, it is not "production quality". If I were to use it in any serious work, I would have made some close-to-surface blocks that I would have fitted perfectly to the airfoil to get a more non-orthogonal mesh close to the surface.
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Old   April 3, 2013, 06:14
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Quote:
Originally Posted by MadsR View Post
Yeah it is mine, trouble is if you have sharp trailing edge. My generator creates o-meshes and expect some bluntness at the TE. If you just click "submit" without submitting any airfoil-data-file, it will default to a mesh for a blunt-TE NACA0015. There is an example airfoil-data-file on the page too.

Mads
I checked your script again and i got nothing.
Profile data is here (there's no sharp edge).

NACA23012.txt

blockMesh file generated by your script here

blockMeshDict.txt

I used default values in your script, except domain radius. I set 5 meters (profile data was in y/c, x/c coordinates)
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Old   April 3, 2013, 06:22
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Quote:
Originally Posted by haakon View Post
If you want to try I have made a C-mesh generator here: https://www.hpc.ntnu.no/display/hpc/...l+Calculations (see bottom of page). It can work with sharp trailing edges. Currently it generates NACA 4-digit airfoil meshes, but as long as you can get a table of coordinates into the script, it will mesh any airfoil with some small modifications.

However, it is not "production quality". If I were to use it in any serious work, I would have made some close-to-surface blocks that I would have fitted perfectly to the airfoil to get a more non-orthogonal mesh close to the surface.
Thanks.

In my C-mesh i have similar blocking structure. It's quite good for simulations. Close-to-surface blocks is a good idea, cause i had problems with this blocking structure. It was solved by adjusting of the edge grading. Some additional blocks could make mesh better definitely but it needs time.
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Old   June 1, 2013, 09:08
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hi skeptik
i want to create a c-mesh in blockmesh but i cant
please can you help me ?
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Old   June 2, 2013, 05:31
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Hi

what is your problem?
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Old   June 2, 2013, 10:01
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hi
i want to creat a c-meh in blockmesh
please please can you help me?
there is this error:
Create time

Creating block mesh from
"/home/shirin/OpenFOAM/shirin-2.1.x/run/tutorials/mesh/snapp/block/constant/polyMesh/blockMeshDict"
Creating curved edges
Creating topology blocks
Creating topology patches

Check topology
#0 Foam::error:rintStack(Foam::Ostream&) in "/opt/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64Gcc46DPOpt/lib/libOpenFOAM.so"
#1 Foam::sigSegv::sigHandler(int) in "/opt/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64Gcc46DPOpt/lib/libOpenFOAM.so"
#2 in "/lib64/libc.so.6"
#3 Foam::blockMesh::checkBlockMesh(Foam:olyMesh const&) const in "/opt/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64Gcc46DPOpt/lib/libblockMesh.so"
#4 Foam::blockMesh::createTopology(Foam::IOdictionary const&, Foam::word const&) in "/opt/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64Gcc46DPOpt/lib/libblockMesh.so"
#5 Foam::blockMesh::blockMesh(Foam::IOdictionary const&, Foam::word const&) in "/opt/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64Gcc46DPOpt/lib/libblockMesh.so"
#6
in "/opt/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64Gcc46DPOpt/bin/blockMesh"
#7 __libc_start_main in "/lib64/libc.so.6"
#8
at /home/abuild/rpmbuild/BUILD/glibc-2.14.1/csu/../sysdeps/x86_64/elf/start.S:116
Segmentation fault
Attached Files
File Type: gz polyMesh.tar.gz (930 Bytes, 1 views)
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Old   June 2, 2013, 11:06
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hi
i can create c-mesh but the block is not correct
please help me
Attached Images
File Type: jpg block.jpg (15.1 KB, 39 views)
Attached Files
File Type: gz polyMesh.tar.gz (854 Bytes, 4 views)
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Old   June 2, 2013, 15:05
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Quote:
Originally Posted by sh.d View Post
hi
i can create c-mesh but the block is not correct
please help me
it seems that you have extra blocks at the tip zone.
you did arc edges, that's right, but there left straigth edges of another block, i see
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Old   June 3, 2013, 03:45
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@Ilya, my simplistic online blockMesh-preprocessor can't handle negative values for the x-coordinate. If you change those three points where x is negative in your airfoil geometry it seems to work.

Just move it a bit out of the positive x-axis to the smallest x-coordinate is zero.

Mads
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Old   June 3, 2013, 03:53
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@Mads
Now it's clear!

Thank you very much. I'll try it little bit later. I think your tool would be very useful.
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Old   June 6, 2013, 08:08
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Quote:
Originally Posted by MadsR View Post
@Ilya, my simplistic online blockMesh-preprocessor can't handle negative values for the x-coordinate. If you change those three points where x is negative in your airfoil geometry it seems to work.

Just move it a bit out of the positive x-axis to the smallest x-coordinate is zero.

Mads
It works fine.
Thank you for your script. It saves time.
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Old   August 2, 2013, 10:30
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Hi dear forumer
i want rotate airfoil in different attack angle but fix the domain and it dont rotate
Can anyone help me?
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Old   August 7, 2013, 02:16
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Quote:
Originally Posted by sh.d View Post
Hi dear forumer
i want rotate airfoil in different attack angle but fix the domain and it dont rotate
Can anyone help me?
look for 'surfaceTransformPoints'. i think it could help you.
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Old   August 7, 2013, 03:20
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@skeptik: Um, did I understand you wrong?: Just change the inlet velocities.

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Old   August 7, 2013, 06:15
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Quote:
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@skeptik: Um, did I understand you wrong?: Just change the inlet velocities.

Mads
Of course, it's reliable way to change flow direction. But if you have a wing in tube, better to change surface position. So it depends from case.
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Old   August 7, 2013, 07:48
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Oh I didn't realise you had your wing in a tube. That's a bit unusual

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