# [ICEM] Uniform mesh in ICEM

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 February 4, 2011, 10:39 Uniform mesh in ICEM #1 New Member   Join Date: Jan 2010 Posts: 15 Rep Power: 7 Hi everybody, How do I get a uniform mesh with hexa elements of the same size in ICEM? My domain has rectangular faces and all the elements are organized so that hexa elements with 2cm side would fit properly. What are the correct parameters to be used? Thanks!

 February 4, 2011, 11:55 #2 Senior Member   AB Join Date: Sep 2009 Location: France Posts: 323 Rep Power: 12 Play with the "Edge Params" option (blocking -> Pre Mesh Params -> Edge Params).

 February 5, 2011, 15:18 Automatic option... #3 Senior Member     Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,662 Blog Entries: 1 Rep Power: 35 Or you could try an automatic Cartesian method such as BFCart... Can you post an image or maybe even your model and I could illustrate...

February 6, 2011, 00:21
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I have attached the model.

The flow enters the domain through an inlet at one extremity, near some obstacles and exit through the other extremity.There's a cubic obstacle downwind the domain. The geometry parts are: INLET, OUTLET, RIGHT, LEFT, TOP and WALLS (which includes the floor and the obstacles surfaces).

What I do in ICEM:

1 - Import the geometry
2 - Create the parts
3 - In Mesh - Global Mesh setup:

a) Global Mesh Parameters: Global element seed size = 0.02m;
b) Shell meshing parameters: Mesh type = All Quad; mesh method = autoblock;
c) Volume mesh parameters: Mesh type = cartesian; mesh method =body-fitted; Aspect ratio 1 1 1;

4 - Compute volume mesh.

The generated mesh is all hexa, but the elements don't have all the same size on each face, while some of them aren't even cubes. Their faces are less than 0.02m.

I would like to get a mesh where every element is a cube with a 0.02m side!

Thanks for any help!
Attached Files
 700-100-100.zip (16.3 KB, 15 views)

Last edited by harerton; February 6, 2011 at 07:33. Reason: adding domain and geometry descriptions

February 19, 2011, 21:14
BFCart.
#5
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Simon Pereira
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You mixed two methods that don't mix. The Cartesian method is a top down method, which means you don't need to start from a surface mesh.

I will attach my tetin file of your model.

Like you, I setup parts and set all the sizes (including the global max size) to 0.02.

Then I made sure the Cartesian meshing parameters were setup and meshed with BFCart...

I got this. (Cutplane shown)

Harerton_BFCart.jpg

I have to say that I think this is not very efficient. Most users prefer to have more elements in the important areas and fewer elements in the less important areas. Uniform density is not what most people are looking for.

This could be very much improved by creating your own cartesian back ground grid with hexa (like is done in the femur tutorial).

If you want, you could also try Octree Tetra followed by a tet to hex conversion (very easy and popular way of getting hexa dominant mesh that transisitions well, converges well, etc.), or perhaps go for full blown hexa blocking (by far the best solution if your real model is this simple).
Attached Files
 700-100-100_BFCART.zip (6.2 KB, 12 views)

February 20, 2011, 09:25
#6
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Quote:
 Originally Posted by PSYMN If you want, you could also try Octree Tetra followed by a tet to hex conversion (very easy and popular way of getting hexa dominant mesh that transisitions well, converges well, etc.), or perhaps go for full blown hexa blocking (by far the best solution if your real model is this simple).
Thank very much for your answer. I know uniform is not the best alternative. But I was trying to find a way to generating it.

Anyway, where do I find this femur tutorial? And are there tutorials for these two alternatives you suggested above (see quote)?

Thanks again!

 February 21, 2011, 01:08 Tutorial. #7 Senior Member     Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,662 Blog Entries: 1 Rep Power: 35 This is a pretty old tutorial (2008 I think)... It was one I quickly put together for a hands on session at a conference... I got some complaints that i didn't include enough detail, such as how to use subsets to get the cutaway mesh views... But hopefully you still get something out of it. I think later the doc people turned it into a real tutorial and put it into the customer portal... You can look for that if you want, but here is my original. ftp://ftp.ansys.com/outgoing/simon/ICEMCFD_Femur.zip In this tutorial, instead of letting the software create its own cartesian background mesh, you can create it... This means you can align it perfectly with your far field (and not have it distort as it projects to surface). You can also used edge parameters to bias along the duct and reduce your mesh count in one direction... Have fun.

 February 21, 2011, 06:16 #8 New Member   Join Date: Jan 2010 Posts: 15 Rep Power: 7 Thanks! Will take a look!

 February 22, 2011, 07:32 #9 New Member   Join Date: Jan 2010 Posts: 15 Rep Power: 7 Simon, Thank you very much for all your help. With the aid of your tutorial I was able to understand more of how ICEM works and I was able to produce a much more improved mesh. Thanks again and keep up the good work! Harerton

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