CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Need how many iteration times

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

LinkBack Thread Tools Display Modes
Old   March 26, 2001, 07:15
Default Need how many iteration times
Harry Qiu
Posts: n/a
Hi,Mr or Mrs:

I'm modeling laminar flame(methane/air).I considered laminar flow, radiation(fluid and solid), chemical reaction.Probably, because the problem is comlex(too many sub-model),no convergence is obtained even if the computer iterates for more than 10,000 times(I note that several handred of iteration time is needed in many FLUENT tuterial guides).Can you tell me that so many iteration times is correct or not?

Thank you very much! Sincerely yours, Harry.
  Reply With Quote

Old   March 26, 2001, 18:45
Default Re: Need how many iteration times
John Patrick
Posts: n/a
I'm modeling flow around a automobile model and on certain boxy designs, convergence establishes at about 1000 iterations, yet on my newest model, a curved design, the convergence state hasn't been achieved yet even at ~200,000 iterations, and residuals keep lowering. So I too am interested in this.

How are iterations measured? Can one apply a time or length to them?

  Reply With Quote

Old   March 26, 2001, 18:59
Default Re: Need how many iteration times
John C. Chien
Posts: n/a
(1). It is one of the most frequently asked question. (2). I don't know whether my experience is applicable to you or not. But I used to read the cfd results into a third party post-processor, where I can put one contour plot on the top of another contour plot at different time (or iteration). (with identical contour levels set for both cases) (3). In this way, you can easily identify whether the steady state has reached or not. At the steady state, you can see only one contour plot, because they are then identical. If not, you can see the areas where they are different. This method should be very accurate. (naturally, it is useless for oscillating flows) I have used the technique for ten years in my own code. (4). Another cheap method is to monitor the flow variable at a fixed point. But then it is hard to see the whole picture.
  Reply With Quote

Old   April 3, 2001, 15:28
Default Re: Need how many iteration times
manaf hasan
Posts: n/a
i am working in fluent about a year and i had this problem of convergense before if the residuals smothly going towards the converganse thats good you can go(but first save your work)incrae under relaxation for all the equations all the reidual will jumb wait for 50-60 iterations to see how this change work this change should slop the residual dowan very fast if that doesnt help moniter your mass inlet and outlet if the risdual is large you have truble in the your mesh. good luck

  Reply With Quote


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
benchmark: flow over a circular cylinder goodegg Main CFD Forum 12 January 22, 2013 12:47
PEM fuel cell long iteration times inoxrocks FLUENT 2 August 7, 2012 07:36
snappyHexMesh aborting Tobi OpenFOAM Native Meshers: snappyHexMesh and Others 0 November 10, 2010 04:23
Parallel runs slower with MTU=9000 than MTU=1500 Javier Larrondo FLUENT 0 October 28, 2007 23:30
Heat exchanger problem chiseung FLUENT 16 October 20, 2001 04:36

All times are GMT -4. The time now is 05:38.