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[snappyHexMesh] SnappyHexMesh for airfoil 2D case: High computational effort for low quality mesh

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Old   October 31, 2014, 11:25
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  #21
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Srsh
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Quote:
Originally Posted by wyldckat View Post
Hi Srsh,


AFAIK, there is no easy way to do this. You'll have to create your own utility to perform this.
There is a utility named plot3dToFoam, which does the opposite of what you're looking for. The source code is located at the path indicated by the following command:
Code:
echo $FOAM_UTILITIES/mesh/conversion/plot3dToFoam
Another utility that you can use as a basis for creating such a new conversion utility is star4ToFoam, whose source code is in the same parent folder as "plot3dToFoam".

Good luck! Best regards,
Bruno
Hello Bruno,

Thank you for your helpful comment. Actually I used writeMeshObj command to transfer mesh to .obj file and after that I wrote a code to change it to plot3d file.

Right now I am dealing with reducing the amount of refinement levels in some part of mesh. I used 4 level of refinement to have fine grids but in some parts having fine mesh is redundant and computationally is time consuming. Do you think SHM has the option to reduce some level of refinement for cut cells? I upload a picture to show what exactly I mean. Thank you so much.

Best regards,
Srsh
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File Type: jpg RefinementM.jpg (29.8 KB, 85 views)
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Old   December 8, 2014, 14:09
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Hi Srsh,

Sorry, my to-do list is getting longer and I'm not finding the time needed to answer everyone

Could you provide a schematic of the mesh you're trying to achieve?

Because from that image, my best guess is that you should be meshing in smaller parts and then merging+stitching the various parts together.

To try and see what I'm referring to, have a look at the images and descriptions on this subsection: http://openfoamwiki.net/index.php/Sn...sBetweenLevels

Best regards,
Bruno
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Old   February 17, 2015, 12:35
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Quote:
Originally Posted by wyldckat View Post
Hi Srsh,

Sorry, my to-do list is getting longer and I'm not finding the time needed to answer everyone

Could you provide a schematic of the mesh you're trying to achieve?

Because from that image, my best guess is that you should be meshing in smaller parts and then merging+stitching the various parts together.

To try and see what I'm referring to, have a look at the images and descriptions on this subsection: http://openfoamwiki.net/index.php/Sn...sBetweenLevels

Best regards,
Bruno
Hello Bruno,

Thank you very much for your response. Actually after generating mesh, in next level I am trying to merge blocks in regions that are not necessary and lower the computational time. I am trying to merge blocks to larger blocks in the regions that I don't care about. For example I attached two pictures which the second one is somehow a desired mesh that I am looking for.
I was wondering if SHM have this option to let me merge blocks to larger blocks after I generate initial grids?

Thank you again,
Srsh
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File Type: jpg refinement by SHM.jpg (28.4 KB, 39 views)
File Type: jpg desired.jpg (15.5 KB, 34 views)
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Old   February 20, 2015, 15:17
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Hi Srsh,

Uhm... be very careful with what kind of mesh refinement transitions you're aiming for... because you're seriously risking having something even worse than this example: http://www.cfd-online.com/Forums/ope...tml#post446350 - read post #17.

Quote:
Originally Posted by blackgalaxy View Post
I was wondering if SHM have this option to let me merge blocks to larger blocks after I generate initial grids?
AFAIK, no, it's not possible to do that. At least not in snappyHexMesh itself. You'll have to do that with mergeMesh and stitchMesh.

The best you can achieve is doing some strategic refinements by using first refineHexMesh or refineMesh and then use snappyHexMesh to remove the cells you don't need.

Best regards,
Bruno
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