[NoradFirst2]

Hello Foamers,

I have quite simple questions to ask but I couldn't find an easy answer.

- Is it possible, using SALOME to create an hybrid mesh (structured hexa mesh for boundary layer and unstructured tetra for the rest)?

- If yes, do you have a guide/tutorial?

- If no, is there an open source soft to do so?

- Can OpenFoam handle such a mesh?

Thanks guys!

[Linse]

Hi James,

I think, all of these are simply answerable with "yes".
- For your hexa boundary layer, you should first produce rectangular 2D meshes on the walls. Then you have to request "viscous boundary layers" for these surfaces during setup of the 3D-meshing.
- For the 3D-meshing, just use a tetra-mesher of your liking for the 3D-process.
- OpenFOAM is well capable of handling such meshes (I have done it myself, already). Just be aware that you will have to use a tool called salomeToOpenFOAM.py (just search in the Salome-forum for it!) for export of an OpenFOAM-mesh. Other methods might not work with the pyramidal cells you will get at the interface between hexes and tetras.

[NoradFirst2]

Thanks for your answers, I will try it this week!

[NoradFirst2]

Can you tell me more about "Then you have to request "viscous boundary layers" for these surfaces during setup of the 3D-meshing." ?

I have a 2D Mesh on my wall using Quadrangle Mapping.

For my overall 3D Mesh, I use 3D-Netgen and I have selected 'Viscous Layer'. I both activated and desativated 'Allow Quadrangle'.

Nothing is happening.

Maybe it comes from my geometry. Let's say you are meshing a cube, you want the bottom face to be 'a wall'. Then you mesh it with 2D Quadrangle. But then, the bottom cells of left/front/right/back faces should be quadrangles and the rest triangles no? Should I do something special about these faces?

Thanks again!

[Linse]

James,

Although the cfd-online forum is quite good and there are many people around, I guess your question would be solved quicker if you put it into the forum on salome-platform.org.

For example at http://salome-platform.org/forum/forum_10/869310111 there is named already one issue which MIGHT be problematic to you as well: Chosing the right height for the "viscous layer". Of course it does not work if the cells would grow out of dimension, i.e. become too big as to be included into the geometry or too big for being seen as subsections of the normal wall cells...

Cheers,
Bernhard

[NoradFirst2]

Originally Posted by NoradFirst2

Can you tell me more about "Then you have to request "viscous boundary layers" for these surfaces during setup of the 3D-meshing." ?

I have a 2D Mesh on my wall using Quadrangle Mapping.

For my overall 3D Mesh, I use 3D-Netgen and I have selected 'Viscous Layer'. I both activated and desativated 'Allow Quadrangle'.

Nothing is happening.

Maybe it comes from my geometry. Let's say you are meshing a cube, you want the bottom face to be 'a wall'. Then you mesh it with 2D Quadrangle. But then, the bottom cells of left/front/right/back faces should be quadrangles and the rest triangles no? Should I do something special about these faces?

Thanks again!

I found the answer I was looking for, here it is if someone is someday reading this thread.

Regarding my cube example, you need to mesh the bottom face with quadrangle (mapping) eg. The other faces should be meshed with whatever (Netgen 2D for example)

For my overall 3D Mesh, I use 3D-Netgen (no need to 'allow quadrangle') and I have selected this optionnal parameter 'Viscous Layer'. Then you select the size and the number of layers (that was okay for me) and finally (what I forgot), you need to select the faces with NO boundary layers - top, left, right, front and back faces in this little case. If you do not do that, Salome will do nothing (in my case).

Thanks for helping guys.