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

Cell Skewness Affect Divergence?

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 24, 2013, 00:40
Default Cell Skewness Affect Divergence?
  #1
Member
 
Join Date: Jan 2013
Posts: 39
Rep Power: 13
pyroknife is on a distinguished road
I used two types of meshing: tetrahedrons and cutcell. I run both under the exact same conditions.
The only difference is the type of mesh (tetraheral vs. cutcell) and the # of elements for each type of mesh and the quality (inherent problems of the type of mesh used).
My solution always diverges when I use the cutcell mesh. I always receive the "temperature is limited to...." during iterations. When I do a case check with the cutcell mesh, i receive the warning that the cell skewness is over the recommended 0.98. I do not receive this warning when I use the tetrahedral mesh.

Is cell skewness really that important? Important enough to cause divergence, particularly in the energy residual?
pyroknife is offline   Reply With Quote

Old   May 24, 2013, 05:49
Default
  #2
Senior Member
 
Lefteris
Join Date: Oct 2011
Location: UK
Posts: 341
Rep Power: 16
Aeronautics El. K. is on a distinguished road
It is very important indeed. Try to refine your mesh or lower the underrelaxation factors and perform more iterations on the pressure correction.
__________________
Lefteris

Aeronautics El. K. is offline   Reply With Quote

Old   May 24, 2013, 17:09
Default
  #3
Member
 
Join Date: Jan 2013
Posts: 39
Rep Power: 13
pyroknife is on a distinguished road
Quote:
Originally Posted by Aeronautics El. K. View Post
It is very important indeed. Try to refine your mesh or lower the underrelaxation factors and perform more iterations on the pressure correction.
Thanks for the reply! What do you mean by "pressure correct?" I am new to ANSYS, so I am not familiar with some of the terms.
pyroknife is offline   Reply With Quote

Old   May 26, 2013, 12:36
Default
  #4
Senior Member
 
Lefteris
Join Date: Oct 2011
Location: UK
Posts: 341
Rep Power: 16
Aeronautics El. K. is on a distinguished road
Pressure Correction has to do with the numerical solution of the problem not with ansys in particular. I suggest that you should study a few things about the SIMPLE method (which you probably use in ansys) before proceeding with your problem.
__________________
Lefteris

Aeronautics El. K. is offline   Reply With Quote

Old   May 27, 2013, 04:10
Default
  #5
New Member
 
Muhammad Aqib Chishty
Join Date: May 2013
Location: Islamabad, Pakistan
Posts: 23
Rep Power: 0
MAC88 is on a distinguished road
Send a message via Skype™ to MAC88
Cell skewness is very important specially when you are working in 3D. I don't know about your case but in 3D, if the cell skewness is above 0.9, then negative volumes are created.
Try to reduce this factor when you are meshing.

Best of luck!
MAC88 is offline   Reply With Quote

Reply


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
interFoam running blowing up sandy13 OpenFOAM Running, Solving & CFD 2 May 5, 2015 08:16
Solution Diverging with Trimmer Mesh rietuk STAR-CCM+ 8 February 27, 2013 05:50
Maximum Cell Skewness killtimm FLUENT 0 June 27, 2010 08:34
cell skewness arunjingade STAR-CCM+ 2 June 23, 2010 08:37
Cells with t below lower limit Purushothama Siemens 2 May 31, 2010 22:58


All times are GMT -4. The time now is 18:23.