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-   -   Mesh stretching starccm+ (http://www.cfd-online.com/Forums/star-ccm/103045-mesh-stretching-starccm.html)

rawe666 June 9, 2012 06:16

Mesh stretching starccm+
 
Hi all,
I am quite new to starccm+ program. What I am trying to do is, generating 2D mesh geometry. I have a simple rectangular geometry. I create it from CAD section in starccm+, mesh it in 3D, then convert it to 2D geometry. I want to stretch my grid points in x- and y- directions. And also I want to use rectangular meshes. Which meshing models should I use and how do I stretch my grid points?

Regards

lava12005 June 20, 2012 05:59

You can use the trimmer mesh model for the rectangular mesh.
I don't think Star-CCM+ can do the stretching that u want (if I get your point).
Trimmer mesh will generate rectangular, but stretching is always a factor of 2.
Or maybe there is a way from the expert here?

Maybe you can just cluster the small box in the area where u want the flow to be resolved and high gradient existance.. and bigger box on the rest..

rwryne June 20, 2012 08:42

Quote:

Originally Posted by lava12005 (Post 367409)
You can use the trimmer mesh model for the rectangular mesh.
I don't think Star-CCM+ can do the stretching that u want (if I get your point).
Trimmer mesh will generate rectangular, but stretching is always a factor of 2.
Or maybe there is a way from the expert here?

Maybe you can just cluster the small box in the area where u want the flow to be resolved and high gradient existance.. and bigger box on the rest..

I hardly ever use the trimmer mesher, but I do know that the volumetric controls for the trimmer mesh has an "isotropic" and "anisotropic" value that you can use to control growth in X and Y.

I assume you can do this without a volumetric control, but do not know how.

lava12005 June 20, 2012 08:52

Quote:

Originally Posted by rwryne (Post 367446)
I hardly ever use the trimmer mesher, but I do know that the volumetric controls for the trimmer mesh has an "isotropic" and "anisotropic" value that you can use to control growth in X and Y.

I assume you can do this without a volumetric control, but do not know how.

Yes, you can do volumetric control and choose anisotropic.
This will help you to locate more points in certain direction, for example when doing ship simulation, one would like to have more points in the vertical direction between the air and water to keep a good resolution at the interface. So we can create a volumetric control near the surface of water, and use the anisotropic option for trimmer mesh and specify the size on vertical mesh direction.

But as far as I know, the jump from let say the smallest dx (say dx1) to the next smallest dx (say dx2) is by the factor of two. So its always dx2 = 2*dx1.

rwryne June 20, 2012 09:31

Quote:

Originally Posted by lava12005 (Post 367449)
But as far as I know, the jump from let say the smallest dx (say dx1) to the next smallest dx (say dx2) is by the factor of two. So its always dx2 = 2*dx1.

Ah, I may have misunderstood the original inquiry. I understand now, thanks for clarification.

rawe666 June 25, 2012 04:08

Quote:

Originally Posted by lava12005 (Post 367409)
You can use the trimmer mesh model for the rectangular mesh.
I don't think Star-CCM+ can do the stretching that u want (if I get your point).
Trimmer mesh will generate rectangular, but stretching is always a factor of 2.
Or maybe there is a way from the expert here?

Maybe you can just cluster the small box in the area where u want the flow to be resolved and high gradient existance.. and bigger box on the rest..

Thank you for your reply. Trimmer --> volumetric control --> anisotropic options allow me to locate more points in specific directions. It is correct. But i couldnt find strecthing factor which I can define. I came to know , you can create one table that contains the coordinates of the points and the number of cells. Then you can create your mesh by choosing the table. However,I have not tried that yet.

NickFSI June 29, 2012 11:08

rawe666, I've been struggling to do the same thing, which I thought was a fairly simple task. Have you had any success with the table method you mentioned?

rawe666 July 2, 2012 09:26

NickFSI, i did not try it. I created my mesh with two volumetric control volumes. In one volume, mesh is finer than the other. It seemed to be easer and it is fine for a now for my case. Good luck!


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