CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   ANSYS Meshing & Geometry (http://www.cfd-online.com/Forums/ansys-meshing/)
-   -   [ICEM] Hybrid mesh (http://www.cfd-online.com/Forums/ansys-meshing/79933-hybrid-mesh.html)

ringtail September 8, 2010 14:01

Hybrid mesh
 
Hi, everybody.

I want to generate a hybrid mesh which is comprised of hexahedra and quad-surface mesh. The computation domain is two dimension, and 2D hexahedra mesh is used in region near the wall. The left domain is filled of quad-surface mesh.

But, I just know how to generate the quad-surface mesh using surface-mesher for 2D compute domain. I don't know how to generate a hybird mesh in which near wall region is replaced by 2D hexahedra mesh.

Anyone could help me?
Thanks.

BrolY September 9, 2010 03:39

Maybe I'm wrong, but for me, 2D hexahedral elements are quad elements.

Why don't you create a full Hexa mesh? If your model isn't too complicated, block it quickly and it would be easier I guess.

ringtail September 9, 2010 12:02

Quote:

Originally Posted by BrolY (Post 274551)
Maybe I'm wrong, but for me, 2D hexahedral elements are quad elements.

Why don't you create a full Hexa mesh? If your model isn't too complicated, block it quickly and it would be easier I guess.

Actually, I have generated a full Hexa mesh. But, unstructured mesh is better for optimization.

BrolY September 10, 2010 03:19

By unstructured mesh, do you mean Tetra mesh?
Otherwise, if it is your blocking that you have converted to an unstructured mesh, this is an Hexa mesh for me ;)

Anyway, do you want to create an hybrid mesh with Tetra and hexa ?

ringtail September 10, 2010 03:34

Quote:

Originally Posted by BrolY (Post 274701)
By unstructured mesh, do you mean Tetra mesh?
Otherwise, if it is your blocking that you have converted to an unstructured mesh, this is an Hexa mesh for me ;)

Anyway, do you want to create an hybrid mesh with Tetra and hexa ?

When I say " structured mesh", I mean Hexa mesh. And unstructured mesh means Tri- or Quad- Surface mesh.

Indeed, I don't know how to generate hybrid mesh with unstructured and structured mesh...

BrolY September 10, 2010 04:18

There is an exemple in the user manual:

Split your geometry in two parts. And create an interface where you have cut your geometry. Mesh your first part with Hexa and your second part with Tetra.
Import the two meshes into the same project.
If you look at your interface, you will see the two meshes on it : tetra and hexa.
You need to merge the two meshes in your interface. For that, use:
edit mesh -> merge nodes -> merge tolerance
For the nodes, select the part interface
For the tolerance, it depends on your model
Select "ignore projection"
Apply

If it is an interface between two fluid, delete the part interface.
Run a check mesh after it. You may have errors such as uncovered faces -> click on solve problems and add the elements to your fluid part.
You may also have errors like non manifold vertices. It means you must refine your hexa and tetra mesh in order to have the same number of nodes on each part of your interface, so all the tetra vertices will find hexa vertices. Got it? Otherwise, you can play on the tolerance. The more you will reduce it, the less non manifold vertices you will find. But I will recommand to create a good mesh on each part of your interface.

I hope it helps ;)

ringtail September 10, 2010 05:11

Quote:

Originally Posted by BrolY (Post 274709)
There is an exemple in the user manual:

Split your geometry in two parts. And create an interface where you have cut your geometry. Mesh your first part with Hexa and your second part with Tetra.
Import the two meshes into the same project.
If you look at your interface, you will see the two meshes on it : tetra and hexa.
You need to merge the two meshes in your interface. For that, use:
edit mesh -> merge nodes -> merge tolerance
For the nodes, select the part interface
For the tolerance, it depends on your model
Select "ignore projection"
Apply

If it is an interface between two fluid, delete the part interface.
Run a check mesh after it. You may have errors such as uncovered faces -> click on solve problems and add the elements to your fluid part.
You may also have errors like non manifold vertices. It means you must refine your hexa and tetra mesh in order to have the same number of nodes on each part of your interface, so all the tetra vertices will find hexa vertices. Got it? Otherwise, you can play on the tolerance. The more you will reduce it, the less non manifold vertices you will find. But I will recommand to create a good mesh on each part of your interface.

I hope it helps ;)

I have read the example, but your explanation is helpful. I will have a try.
I think the difficulty may be that the geometry is a little complex, it's a high lift device.

Thank you

sidspark12 September 10, 2010 05:56

whenever v r talking about the hybrid mesh.........that means it is the combination of tetra and hex mesh for 3D geometry........and tri + quad for 2D geometry.........here you are talking about quad + hex , so i think this is not the hybrid mesh case.........hex mesh in 2D is called as quad mesh...........:)

sidspark12 September 10, 2010 05:59

one more thing......if the geometry is simple.......then go for hex mesh...........but if it is complex then that time u have to do the hybrid meshing.........devide the geometry in no. of volumes according to ur convenience and then go for mesh.........may b this ll give u better result with less memory uses...........:rolleyes:

ringtail September 10, 2010 07:44

Quote:

Originally Posted by sidspark12 (Post 274723)
whenever v r talking about the hybrid mesh.........that means it is the combination of tetra and hex mesh for 3D geometry........and tri + quad for 2D geometry.........here you are talking about quad + hex , so i think this is not the hybrid mesh case.........hex mesh in 2D is called as quad mesh...........:)

I dont think so...
When I said quad mesh, actually, I mean the mesh generated through mesh->compute mesh->surface mesh.
And hex mesh is the one generated by blocking.

What's more, the mesh is 2D.

sidspark12 September 10, 2010 12:07

hello ringtail......yes u r exactly right.........now when i translate this mesh in perpendicular direction to 2d mesh.....that will be the 3d mesh and that will be hex mesh......

PSYMN December 5, 2010 21:11

No idea...
 
Wow, this is a confusing thread...:eek:

I still have no idea what you want ;)

Are you all set now?

vmlxb6 March 5, 2011 13:36

@ Simon and Broly
 
@ Broly: I got stuck in the first step itself. How do you split your geometry. Do you have to build a separate geometry ??

@ Simon: could you please help me with this thread

http://www.cfd-online.com/Forums/ans...brid-mesh.html

Its a pretty simple geometry but am unable to do it.

Thank you. Appreciate your help.

BrolY March 7, 2011 04:27

Geometry -> Create/modify Surface -> Segment / Trim Surface
You should try to play with those options to learn how they work.
Good luck !


All times are GMT -4. The time now is 07:14.