CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > ANSYS Meshing & Geometry

[ICEM] Tetra boundary layer

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 23, 2013, 16:52
Default Tetra boundary layer
  #1
New Member
 
Join Date: Jan 2013
Posts: 4
Rep Power: 13
mario1701 is on a distinguished road
Hi,

I have to create a tetra boundary layer around a high-speed train in ICEM and I wondering what is the best way to do it - so far, I have read just about hybrid meshes or prism boundary layers (as I have mentioned before - it has to be tetra mesh). I would be very grateful for any smart methods.

Mario
mario1701 is offline   Reply With Quote

Old   January 23, 2013, 17:24
Default
  #2
Far
Senior Member
 
Sijal
Join Date: Mar 2009
Location: Islamabad
Posts: 4,558
Blog Entries: 6
Rep Power: 54
Far has a spectacular aura aboutFar has a spectacular aura about
Send a message via Skype™ to Far
1. tetra size ratio

2. tetra width


Far is online now   Reply With Quote

Old   January 23, 2013, 19:39
Default
  #3
Super Moderator
 
diamondx's Avatar
 
Ghazlani M. Ali
Join Date: May 2011
Location: Tokyo, Japan
Posts: 1,385
Blog Entries: 23
Rep Power: 29
diamondx will become famous soon enough
sorry for jumping in, i have a question in the surface mesh tab, what does tetra width useful for ???
__________________
Regards,
New to ICEM CFD, try this document --> https://goo.gl/KAOIwm
Ali
diamondx is offline   Reply With Quote

Old   January 23, 2013, 19:51
Default
  #4
Super Moderator
 
diamondx's Avatar
 
Ghazlani M. Ali
Join Date: May 2011
Location: Tokyo, Japan
Posts: 1,385
Blog Entries: 23
Rep Power: 29
diamondx will become famous soon enough
i have chaging it but nothing change ??
__________________
Regards,
New to ICEM CFD, try this document --> https://goo.gl/KAOIwm
Ali
diamondx is offline   Reply With Quote

Old   January 23, 2013, 23:42
Default
  #5
Far
Senior Member
 
Sijal
Join Date: Mar 2009
Location: Islamabad
Posts: 4,558
Blog Entries: 6
Rep Power: 54
Far has a spectacular aura aboutFar has a spectacular aura about
Send a message via Skype™ to Far
Quote:
Originally Posted by diamondx View Post
i have a question in the surface mesh tab, what does tetra width useful for ???
Quote:
Originally Posted by diamondx View Post
i have chaging it but nothing change ??
It is working when you define the tet width and ratio for the volume meshing. It applies these settings on volume and surface. But only for surface meshing, I dont think they have any effect.

Last edited by Far; January 24, 2013 at 00:26.
Far is online now   Reply With Quote

Old   January 24, 2013, 09:12
Default
  #6
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,663
Blog Entries: 1
Rep Power: 47
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
Tetra width specifies the number of elements into the volume before the tetra ratio starts to expand the mesh. It only works with Octree Tetra.

If I had a surface size of 2 and a max size of 64 and a tetra width of 3, I would get at least 3 layers of size 2 volume mesh before the mesh started to expand up to the max size.

It is like putting a mesh density region near the surface, and in fact, works the same way in the back ground.
__________________
-----------------------------------------
Please help guide development at ANSYS by filling in these surveys

Public ANSYS ICEM CFD Users Survey

This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)...

CFD Online Users Survey
PSYMN is offline   Reply With Quote

Old   January 26, 2013, 11:04
Default
  #7
New Member
 
Join Date: Jan 2013
Posts: 4
Rep Power: 13
mario1701 is on a distinguished road
Thank you very much for reply, but in case of using wall functions, it doesn't influence the results (y+ is not decreasing). I thought rather about characteristic "elongated" shape, which can be obtained with use of the prism mesh. Maybe I should create such a prism mesh and then convert it into a tetra mesh?
mario1701 is offline   Reply With Quote

Old   January 26, 2013, 11:09
Default
  #8
Far
Senior Member
 
Sijal
Join Date: Mar 2009
Location: Islamabad
Posts: 4,558
Blog Entries: 6
Rep Power: 54
Far has a spectacular aura aboutFar has a spectacular aura about
Send a message via Skype™ to Far
Are you using scalable wall functions? What is the minimum wall Yplus in your simulations?

I think prisms are better than tetras
Far is online now   Reply With Quote

Old   January 26, 2013, 18:11
Default
  #9
New Member
 
Join Date: Jan 2013
Posts: 4
Rep Power: 13
mario1701 is on a distinguished road
I was using standard wall functions. Unfortunately, I have to use tetras (I use some special applications developed at my university that need tetra meshes). Y+ is still huge - on mesh of 126k nodes I have minimal y+ on the surface of locomotive equal approximately 2e3.
mario1701 is offline   Reply With Quote

Old   January 27, 2013, 02:23
Default
  #10
Far
Senior Member
 
Sijal
Join Date: Mar 2009
Location: Islamabad
Posts: 4,558
Blog Entries: 6
Rep Power: 54
Far has a spectacular aura aboutFar has a spectacular aura about
Send a message via Skype™ to Far
are you sure about units of your model?

Another option is to use the T-Rex type algorithm!!!
Far is online now   Reply With Quote

Old   January 27, 2013, 13:04
Default
  #11
New Member
 
Join Date: Jan 2013
Posts: 4
Rep Power: 13
mario1701 is on a distinguished road
When it comes to the units - everything seems to be correct. The mesh was created in [mm] and is correctly read by fluent (the main dimensions are presented in meters, but are for sure correct). I tried to create a prism boundary layer and then converted it to tetra - y+ decreased signifficantly, but the quality of the worst element is quite low (I am not sure if 0.05 - 0.1 for 15% of elements is a reasonable level - but maybe for boundary layer it does not matter (large pressure changes just in normal direction)?). ICEM does not support T-Rex, does it?
mario1701 is offline   Reply With Quote

Old   February 6, 2013, 10:54
Default
  #12
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,663
Blog Entries: 1
Rep Power: 47
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
Sure, use prisms to get the Y+ you want and then use the Edit mesh option to change mesh type and covert all to Tetra...
__________________
-----------------------------------------
Please help guide development at ANSYS by filling in these surveys

Public ANSYS ICEM CFD Users Survey

This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)...

CFD Online Users Survey
PSYMN is offline   Reply With Quote

Old   September 12, 2014, 10:56
Default Transition between finer and coarse mesh zones
  #13
New Member
 
Roberto Meloni
Join Date: Dec 2012
Posts: 14
Rep Power: 13
Roberto Meloni is on a distinguished road
Hi All.
I have a problem with a mesh I’m trying to build and I wonder if you can help me to solve it.
My problem is that I can’t define a proper transition between finer zones of the model and the coarse ones. I set up specific part size for the surfaces as well as for tetra size ratio, but it seems not to work fine. I believe that the system doesn’t respect the mesh size of the mesh I specify on the surface, but it builds a very finer mesh.
I’am meshing with the following setting:
- Robust(Octree);
- Patch Independent
- In the Global Mesh Size panel, I enable the Curve/proximity based refinement
The high density zones you can see from the picture refer to small holes. I have to mesh them with a very fine mesh (0.17 mm). The red zone refer to the core region of the model.

Could you please help me?
Best regards,
Roberto.
Attached Images
File Type: jpg Untitled.jpg (90.9 KB, 43 views)
Roberto Meloni is offline   Reply With Quote

Reply

Tags
boundary layer mesh, icem 3d, tetra mesh

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[snappyHexMesh] No layers in a small gap bobburnquist OpenFOAM Meshing & Mesh Conversion 6 August 26, 2015 10:38
Grid Independence of Boundary layer Luigi_ Main CFD Forum 0 December 14, 2011 14:42
3D Boundary Layer Mario FLUENT 0 February 17, 2009 04:40
[Commercial meshers] Trimmed cell and embedded refinement mesh conversion issues michele OpenFOAM Meshing & Mesh Conversion 2 July 15, 2005 05:15
boundary layer thickness 98.4F Main CFD Forum 1 December 29, 2000 08:23


All times are GMT -4. The time now is 00:01.