CFD Online Discussion Forums

CFD Online Discussion Forums (
-   ANSYS Meshing & Geometry (
-   -   [ICEM] Box for Boundary Layer (

FabioT August 20, 2010 18:49

Box for Boundary Layer
Hi everybody. I am a beginner and I have a really simple question.

I have a box and I need to mesh it to simulate with fluent the wind flow. The box is empty, only air.

I want to see the boundary layer in Fluent, therefore I want the mesh to be finer close to the bottom and coarser close to the roof.

I don't understand how to do it. I made some attempts with some mesh laws but it didn't work because even when I change some parameters (for instance spacing 1 and 2 and number of nodes of an edge) they don't change.

Hope my problem is clear.

Btw, if somebody can give me a tutorial also for the boundary layer in fluent it would be really useful for me.



FabioT August 23, 2010 16:59

Please! I don't think I'm asking something impossible.
Is the question clear?

If it is and the answer is really easy please post it anyway because I really need it for college.

Thank you very much everybody,


FabioT August 23, 2010 19:08

1 Attachment(s)
Ok, I think i managed to represent what I wanted. But only for the premesh.

See attachment.

Now the problem is that I don't know how to compute the real mesh so that it will be like the premesh. Now it always gives me back a constant mesh.



BrolY August 24, 2010 03:21


Changing the number of nodes on your edges should work.
I think it doesn't work for you because you tried to change the number of nodes on every edges at the same time.
Some edges are linked in ICEM. So if you change the number of nodes on your bottom curves, it could also change the number of nodes on your top curves (I'm not an exert with ICEM Hexa but I have noticed that sometimes). So you should change the number of nodes on your bottom curves first in order to refine the mesh in this area and see what it's doing.

If you want to create a "real" mesh, right click on "Pre mesh" and left click on "Convert to unstructured".

Good luck !

EDIT: I got a better look at your image, and I have seen that you have only one edge in the Y direction. You could use the exponential1 law and play with the spacing 1 and 2. You could use a very small number fo the spacing 1 and a bigger one for the spacing 2. Try to play with those numbers.

BrolY August 24, 2010 06:33

1 Attachment(s)
Here is an image to give you an example

PSYMN August 24, 2010 09:57

File menu => Mesh => Load from blocking...

If you have the premesh, you just need to convert it into an unstructured mesh.

Right click on premesh in the model tree and choose "convert to unstructured mesh", or go into the File menu => Mesh => Load from blocking...

This will give you the unstructured mesh that you can then output to Fluent.

Having said that, you really need to try a couple Hexa tutorials. It is a bit of extra time up front, but you would make up for it with time saved on your real models and in reduced frustration.


All times are GMT -4. The time now is 22:35.