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

[ICEM] Non-Positive Volumes Exist: Importing to FLUENT

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

Like Tree1Likes
  • 1 Post By VT_Bromley

Reply
 
LinkBack Thread Tools Display Modes
Old   August 30, 2011, 23:05
Default Non-Positive Volumes Exist: Importing to FLUENT
  #1
New Member
 
Michael
Join Date: Nov 2010
Posts: 23
Rep Power: 6
VT_Bromley is on a distinguished road
Hey all,

I'm trying to import a grid into FLUENT and I'm constantly getting the following two warnings:

Warning: non-positive volumes exist.

Warning: non-positive face area exist.

However when checking my grid in ICEM it does not show negative values for either of these.


To quickly explain my mesh. The bottom rectangular box is full of a solid, the middle rectangular box is air initially with a ramp labeled in red. The small rectangle at the top is a porous zone. The wall facing you in light blue is a symmetry wall. My origin (0,0,0 point) is at the bottom left corner of the "air" region.

I have checked everything in ICEM and it all seems to check out, however once it is imported into FLUENT it has the above warnings. Any ideas on where to go from here?
hossein65 likes this.
VT_Bromley is offline   Reply With Quote

Old   February 24, 2012, 03:44
Default
  #2
New Member
 
Hossein
Join Date: Oct 2010
Location: Greensboro, NC, USA
Posts: 24
Rep Power: 6
hossein65 is on a distinguished road
Dear all,
I got such a problem! please help!
hossein65 is offline   Reply With Quote

Old   February 24, 2012, 04:51
Default
  #3
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,914
Blog Entries: 6
Rep Power: 38
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
locate the negative volume and remove it
Far is offline   Reply With Quote

Old   February 26, 2012, 01:39
Default
  #4
New Member
 
william
Join Date: Feb 2010
Posts: 11
Rep Power: 7
faee0 is on a distinguished road
the mesh is too bad!you must remesh it
faee0 is offline   Reply With Quote

Old   February 26, 2012, 02:10
Default
  #5
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,914
Blog Entries: 6
Rep Power: 38
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Quote:
the mesh is too bad!you must remesh it
Well that is obvious, but it may be due to some local regions e.g. at sharp corners or topology may not be correct. Therefore it is better to locate the problem area and remove that problem. It is also better for future work on similar geometries.
Far is offline   Reply With Quote

Old   April 26, 2012, 10:56
Default
  #6
New Member
 
Zhonghai Xu(xuzhonghai@sjtu.edu.cn)
Join Date: Apr 2012
Location: Shanghai,CHINA
Posts: 17
Rep Power: 5
realstoneman is on a distinguished road
dear Far
I have the same problem,when I import my mesh into Fluent ,get a warning:non-positive volumes exist.I just have learn ICEM for some weeks,and I don't konw how to locate the negetive volumes as you said above.Please help me,by the way,can I just use the"edit mesh-->smooth elements globally" to smooth the mesh?
May I have you email?
realstoneman is offline   Reply With Quote

Old   April 26, 2012, 14:16
Default
  #7
New Member
 
Hossein
Join Date: Oct 2010
Location: Greensboro, NC, USA
Posts: 24
Rep Power: 6
hossein65 is on a distinguished road
I could solve my problem by coarsening the mesh . You know, using a smaller mesh size can help very much. try it!
__________________
Hossein Amini
PhD student in Biochemical Engineering; Computational Science and Engineering department;
North Carolina Agricultural and Technical State University
hossein65 is offline   Reply With Quote

Old   April 27, 2012, 08:35
Default
  #8
Member
 
jeevan kumar
Join Date: Mar 2009
Posts: 81
Rep Power: 8
jeevankumarb is on a distinguished road
Hello Michael,

The way the quality measured in fluent is different form the way it is in Fluent. For fluent at least you need minimum quality of 0.05(ICEM) but still you might face problems in convergence.
From the image it seems that your topology is very bad. You have to change the topology. Just play with the blocking and thing some topologies which can give good quality mesh. Thats how you learn and expertise ICEM.

Regards
jeevankumarb is offline   Reply With Quote

Old   April 28, 2012, 11:01
Default I search for help
  #9
New Member
 
Zhonghai Xu(xuzhonghai@sjtu.edu.cn)
Join Date: Apr 2012
Location: Shanghai,CHINA
Posts: 17
Rep Power: 5
realstoneman is on a distinguished road
hello,
I created a mesh by ICEM CFD,but I don't know why my grids have something wrong,the attachment is the part where I found.The vertical line with 5 nodes,but why don't they maintain horizontal and merge into the line below it?
And the second picture,you can see two lines stand together,the two problems have driven me mad!!!!
Could you help me with the problem?
Thanks very much~
PS:the model I created is symmetrical,but the other side is OK,I don't know why.

May I have your email?Mine is xufei_0322@foxmail.com I wish I could communicate with you.
Attached Images
File Type: jpg 20120427_fb9656f3b42a186d4c0a4bOmQSICtt8P.jpg (20.8 KB, 30 views)
realstoneman is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Grid check failed (non positive volumes). Muhammad Usman Qureshi FLUENT 5 September 26, 2013 06:26
importing .stl file to Fluent snudurupati FLUENT 0 July 15, 2009 11:21
Importing Fluent polyhedral meshes fra76 OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 2 October 11, 2008 04:44
Exporting Fluent results and importing into StarCD Jim Loebig FLUENT 0 July 20, 2007 16:26
Importing a structured mesh into Fluent Flav FLUENT 0 November 30, 1999 11:57


All times are GMT -4. The time now is 09:37.