CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > Siemens

High residuals

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

LinkBack Thread Tools Search this Thread Display Modes
Old   November 25, 2008, 14:26
Default High residuals
Posts: n/a
Hello, I have a new question for You, in my simulation of wing in free flux, the residual are high but the result in terms of Cl and Cp is good which it is the reason?

  Reply With Quote

Old   November 25, 2008, 23:17
Default Re: High residuals
no one
Posts: n/a
The magnitude of the residuals is not important, they are pretty arbitrary. I think Star-CD and Star-CCM+ normalize your residuals by the largest change in any cell from iteration 0 to iteration 1. If the initial conditions were very close to the solution, then your residuals will be normalized by a very small number, making the residuals high. The thing to look out for is increasing or oscillating residuals that could indicated mesh or setup problems. Monitoring values like Cp and Cl as you have done is a much better gauge of convergence. Residuals are a better indicator of mesh quality than convergence.
  Reply With Quote

Old   November 26, 2008, 04:43
Default Re: High residuals
Posts: n/a
Thank you very much hour I am most calmer

  Reply With Quote

Old   November 26, 2008, 09:19
Default Re: High residuals
Posts: n/a
At least in 3.26 you can turn ANORM on.

This turns the residual methodology back to the former physics based system, used before they decided that they needed to be like Fluent.

For most of the variables this ends up being the sum of all fluxes through the cell walls normalized by the inlet flux.

The absolute value is related to the inlet flux to volume of the model, but at least it means something physical.

I believe they changed because Fluent was 'easier' and 'faster' to converge. Since you have no real idea what these numbers mean if the number was low then you can pretend that it is converged if it asymptotes.

It is somewhat strange that if you have a bad initial guess you can converge faster (fewer iterations) than if you mapped a full solution. In the first case the initial residuals are very poor and can be reduced fast, in the second case you may be very near convergence and thus they should not change much.

  Reply With Quote

Old   April 20, 2020, 12:14
New Member
Roger Fernandes
Join Date: Jun 2019
Posts: 5
Rep Power: 6
Rogerfdp is on a distinguished road
Besides simulating a lot and learning Is there any literature that can be recommended on this?
Rogerfdp is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Residuals converged but high Gilles CFX 2 September 30, 2008 20:05
help high initial residuals Aly FLUENT 0 October 11, 2007 10:04
Help HIGH RESIDUALS Aly Fidelity CFD 0 October 11, 2007 09:57
residuals Karl CFX 2 June 25, 2003 00:13
residuals andrea Siemens 0 March 6, 2002 10:41

All times are GMT -4. The time now is 01:12.