CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

Grid quality in CFX4.2

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 24, 1999, 06:05
Default Grid quality in CFX4.2
  #1
P. Adamsen
Guest
 
Posts: n/a
I hope you can help me with me question. I have been running a test in CFX4.2 where I used a Poiseuille flow. I meshed the tube with an O-grid patched to an H-grid (i.e. Butterfly grid). But the numerical result deviates from the analytical fully developed profile in the block corners, where the two grids are patched together. This gets even more clear when I look at the velocity gradients for the same region.

And now to my question: Is this due to the fact that the control volumes contain a larger angle the closer one gets to the block corners, or is there some other explanation?
  Reply With Quote

Old   November 24, 1999, 20:17
Default Re: Grid quality in CFX4.2
  #2
John Chien
Guest
 
Posts: n/a
(1). A couple of exercises you can do. (2). The first: change the relative size of the two regions, and check the result to see if it is always happen at the same location. (3). The second: reduce the mesh size (especially the one at the corner) and verify the mesh independent solution. That is, will the solution converge to the analytical solution as the mesh size is reduced. (4). If your current solution is not mesh independent, then you should have some kind of errors. It is nothing unusual. (5). It is important to know the total number of mesh points needed to get the mesh independent solution. (6). There is no way one can evaluate the accuracy of solution based on the finite size mesh. (unless the solution is constant or linear.)
  Reply With Quote

Old   November 25, 1999, 13:32
Default Re: Grid quality in CFX4.2
  #3
J. Y. Luo
Guest
 
Posts: n/a
This is a very common meshing practice - if the discretisation is done properly, then you should not see what you saw. Ask the CFX support engineers to see they can fix for you.
  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
Standard procedure to check grid quality in Gridgen software CFD XUE FLUENT 1 March 21, 2011 15:56
Improve smoothness & quality of structured grid quarkz Main CFD Forum 2 March 10, 2007 16:26
Negative quality elements in ICEM Grid Kartik CFX 2 June 17, 2005 05:45
Combustion Convergence problems Art Stretton Phoenics 5 April 2, 2002 05:59
Grid Quality and the Solution Faraz Main CFD Forum 4 January 10, 2000 19:18


All times are GMT -4. The time now is 05:33.