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Duct Mesh control of surface meshes

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Duct Mesh control of surface meshes

Posted by julien at March 16. 2019

Hello,

 

I want to mesh a duct where I need to define different grid sizes along the external wall (external wall is composed of 3 surfaces). My geometry is only the half duct considering the symmetry plane.

My goal is to preprocess a mesh for Openfoam fluid flow simulation. So I need to avoid the more that I can tets mesh because of non orthogonality issues.

Of course I cannot use directly Hexa mesh due to the inlet and outlet surfaces geometry not compatible with hexa mesh.

I have already mesh some cases with extrusion meshes tools along duct length but now I have different surfaces along the duct, so I cannot use extrusion. I will not be able to select surface mesh groups for applying boundary conditions in Openfoam.

I try to do the following solution: To have a better control on the number of cells, I want to use quadrangle mapping where I can impose the number of nodes along the length of the duct on the 3 different surfaces. So I have 3 mapped meshed surfaces with conformal meshes. See attached picture

Next step is my problem, my plan was to use the 3 surfaces meshes with the option "import 1D-2D elements from another mesh" in a 3D netgen tets but it seems that it is not compatible. Maybe I need to convert surface mapped meshes into triangular elements before netgen generation? How can I do that?

What is your advice? need some help.

Best regards

Julien

 

 

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Re: Duct Mesh control of surface meshes

Posted by julien at March 16. 2019

Ok, I reconsider my problem. I have discover the utility divided disk in geometry module. So now I go for mesh with hex volume. So now inlet and outlet surfaces are no more a problem.

The remaining problem is how to deal with external wall surfaces, I don't know how to create the whole hex mesh in only one volume with the 3 external surfaces. I only see the solution to have 3 volumes...

How can I manage to have only one final mesh if I have to split into 3 volumes? Is it possible to fuse the 3 meshes in one?

Best regards

Re: Duct Mesh control of surface meshes

Posted by julien at March 16. 2019

Hi,

I found that it is possible after create compound, that I can merge the volume group!

Close to the goal, but when I export my geometry in Openfoam I have warnings of default faces not attributed.

I have created meshes with exactly the same parameters on the different portions of the duct but I see that there is some narrow differences between shared surfaces.I have a closer look on the merge mesh and I see that there is some very little differences between nodes.

Paraview visualisation give me the same result. 4 new surfaces are created between shared surfaces

How can I have exactly the same surfaces. I have a look on copy mesh utility but I am not able to use it.

Any ideas?

Best regards

Re: Duct Mesh control of surface meshes

Posted by julien at March 16. 2019

See inside the duct between 2 merged parts

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Re: Duct Mesh control of surface meshes

Posted by Saint Michael at March 18. 2019

Hi Julien

As far as I understand, you have a duct with 3 surfaces along it. It's not an obstacle for Extrusion 3D algorithm. You only need to make quadrangle mesh on inlet or outlet surfaces. To get it, you can use Divided disk to get such a mesh in a separate mesh object, and then use Import 1d2D algo to obtain these quadrangles in the duct mesh.

Try an attached script.

St.Michael

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Re: Duct Mesh control of surface meshes

Posted by julien at March 22. 2019

Thank you St.Michael,

I resolved my problem, the boundary layers meshes had a warning, so I modified BL parameters and now it works fine.

Your solution asks to have 3 different volumes, make 3D extrusion with using Import 1d2D algo, create compound and merge volumes groups ? 

Best regards

Julien

 

Re: Duct Mesh control of surface meshes

Posted by Saint Michael at March 22. 2019

My solution is for a prismatic solid with composite walls.

St.Michael

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