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[mesh manipulation] Having difficulties using refineMesh and mesh refinement

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Old   April 19, 2016, 09:36
Default Having difficulties using refineMesh and mesh refinement
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Eduardo Firvida
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Hi I have the current blockMesh file, and I want to refine this mesh along the `x` and `y` axis, I have no problem with the z axis.
If I increment the blocks resolution of the mesh along the z axis the checkMesh utility say that the mesh its OK. for finer mesh and coarse mesh along this axis.
If I increment the mesh resolution along the `x` or `y` axis the checkMesh throws errors. so I think that increase the blocks resolution its not the solution, and I want to try using the refineMesh utility, to see what's happen. But I donít have any idea how to use it, I search for the web and see that a refineMeshDict is needed, but the first parameter of the dict is a set of cells to be refined and I donít know haw to create it.

So I really do not know what is the best choice for refine my mesh and how to do it, please any help?

thanks for all
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File Type: zip blockMeshDict_(z_axis_finer).zip (102.0 KB, 60 views)
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Old   April 26, 2016, 05:41
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Hi,

nice blockMesh work. Crazy never saw such stuff in blockMesh before. Why are you doing that? You want to parameterize you blockMeshDict? If not the work was not worth (in my opinion). Simple and easy meshing would be, STL + snappyHexMesh. Done in a few minutes.

Anyway. I will not check your blockMeshDict further because it is really "blockMesh beyond the scope".

To your problem. If you want to refine in x,y direction you really have to figure out which block you have to modify that in each block the amount of points are equal.


My suggestion (although you investigated a lot of time into your blockMeshDict), throw it away and use snappyHexMesh + Layer. It is easier, and you have a lot of freedom in refining regions etc.
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Old   April 26, 2016, 08:20
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Quote:
Originally Posted by Tobi View Post
Hi,

nice blockMesh work. Crazy never saw such stuff in blockMesh before. Why are you doing that? You want to parameterize you blockMeshDict? If not the work was not worth (in my opinion). Simple and easy meshing would be, STL + snappyHexMesh. Done in a few minutes.

Anyway. I will not check your blockMeshDict further because it is really "blockMesh beyond the scope".

To your problem. If you want to refine in x,y direction you really have to figure out which block you have to modify that in each block the amount of points are equal.


My suggestion (although you investigated a lot of time into your blockMeshDict), throw it away and use snappyHexMesh + Layer. It is easier, and you have a lot of freedom in refining regions etc.
Hi Thanks for your reply, I have tried with the snappyHexMesh before try the blockMesh, and yes, I need to use the blockmesh because I need a parametric and structured mesh because the previous test simulations give me best results with structured meshes than the mesh generated with snappyHexMesh
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Old   April 26, 2016, 08:52
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SnappyHexMesh makes hybrid meshes. I think you forgot the layers or you are not familiar with snappyHexMesh and meshing using that tool? If you do not change your geometry, then snappyHexMesh would be my favorite in any case. Anyway I think you know what you do (:

So good luck in proceeding with your blockMeshDict.


PS: It is clear why structured meshes will give better results (numerics) but handling your blockMeshDict is in my opinion crazy (:
I think that if you have a good mesh with snappyHexMesh, you could also achieve the results you get using a structured grid.
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Old   April 26, 2016, 11:12
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Quote:
Originally Posted by Tobi View Post
SnappyHexMesh makes hybrid meshes. I think you forgot the layers or you are not familiar with snappyHexMesh and meshing using that tool? If you do not change your geometry, then snappyHexMesh would be my favorite in any case. Anyway I think you know what you do (:

So good luck in proceeding with your blockMeshDict.


PS: It is clear why structured meshes will give better results (numerics) but handling your blockMeshDict is in my opinion crazy (:
I think that if you have a good mesh with snappyHexMesh, you could also achieve the results you get using a structured grid.
That is the problem I'm generating my geometry dynamically, of course I didnít do this manually, I'm making a tool to generate OpenFoam cases, and I need that the tool to be as generic as possible. something like https://sourceforge.net/projects/bladedesigner/ but not so complicated.

Thanks again I will continue breaking my head
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Old   April 26, 2016, 11:26
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I know a answer I will make a thread for that
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Old   April 26, 2016, 13:08
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Quote:
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I know a answer I will make a thread for that




I'll wait for that thread
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Old   April 26, 2016, 13:29
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Here we go:

http://www.cfd-online.com/Forums/ope...tml#post596817
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Old   April 26, 2016, 14:58
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Many Thanks!
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