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

what should I do if the solution didn't converge?

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 7, 2004, 10:04
Default what should I do if the solution didn't converge?
  #1
Beeny
Guest
 
Posts: n/a
hi all!

If the solution (mass) didn't converge, what in general should I do to check it and amend it?

Benny
  Reply With Quote

Old   April 7, 2004, 11:04
Default Re: what should I do if the solution didn't conver
  #2
John
Guest
 
Posts: n/a
try changing the termination restriction in Solve..>Controls..>Multigrid from it's default value 0.1 I Think to 0.001.

bye
  Reply With Quote

Old   April 7, 2004, 18:57
Default Re: what should I do if the solution didn't conver
  #3
ap
Guest
 
Posts: n/a
First of all, try to reduce under-relaxation factors a bit. If this is not enough, try to obtain a solution using the first order discretization scheme, then switch to higher order.

Also a good quality grid and proper boundary conditions are required to get good convercence rate.

Hi

ap
  Reply With Quote

Old   July 27, 2011, 10:36
Default
  #4
New Member
 
Nitin
Join Date: Jul 2011
Posts: 2
Rep Power: 0
rob sharma is on a distinguished road
Guys i have a big problem like my solution is not converging in simple case. I have a pipe 800 mm lenth and 15 mm dia. I am using axis-symmetric pipe. I simulate that pipe with inlet velocity 0.486 by using 800 nodes in length and 8 in readiusof pipe for laminar flow. It is simulated at around 246 iterations. But after after increasing nodes in length that is of 1200 and 10 in radius of pipe, it does not converger. If i give initail velocity less like 0.470, then it converges. But the result does not come appropriate. all my values come under the convergence criterion of 0.001. but the continuity does not come. i dont know what to do. If anybody tell me i will bw very thankful...kindly...
rob sharma is offline   Reply With Quote

Old   August 13, 2011, 00:31
Default
  #5
Senior Member
 
teguhtf's Avatar
 
teguh hady
Join Date: Aug 2009
Location: Saga, Japan
Posts: 222
Rep Power: 18
teguhtf is on a distinguished road
Hi Rob,
I think the convergence of simulation based on:
1. Complexity of geometry
2. Mesh size, quality.
3. the precision of the simulation (single or double)
4. Turbulence model choice
5. Discritization method (first order,second order and so on)
6. Our physical input
7. setting under relaxation factor (the setting of under relaxation factor is depend on gauss seidel method)
I think you can analyze your case based on those things.
Hope it helps
teguh
__________________
Now Or Never!!!
teguhtf is offline   Reply With Quote

Old   August 13, 2011, 07:09
Default convergence problem
  #6
New Member
 
Nitin
Join Date: Jul 2011
Posts: 2
Rep Power: 0
rob sharma is on a distinguished road
Its a laminar flow with 1200 nodes in length and 10 in radius. Anyone could suggest me the book or reason why does the solution not converge. I need to know the reason.....kindly please help me.......
rob sharma is offline   Reply With Quote

Old   August 27, 2011, 01:04
Default
  #7
Senior Member
 
teguhtf's Avatar
 
teguh hady
Join Date: Aug 2009
Location: Saga, Japan
Posts: 222
Rep Power: 18
teguhtf is on a distinguished road
He there,
For internal flow, i think you should choose turbulent mode. because, i think there will be little turbulence generated near the wall. If you're sure that there is no turbulence, you can choose laminar mode.
Teguh
__________________
Now Or Never!!!
teguhtf 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
Naca 0012 (compressible and inviscid) flow convergence problem bipulsaha FLUENT 1 July 6, 2011 08:51
simple algorithm, converge of solution bbasal Main CFD Forum 0 February 13, 2010 03:58
Solution Does Not Converge Rif Main CFD Forum 3 March 7, 2008 06:33
My Solution wont Converge!!! Chris FLUENT 6 April 16, 2005 19:57
what to do when solution doesn't converge? Jenny CFX 5 January 28, 2004 05:00


All times are GMT -4. The time now is 14:56.