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

Is this solution converged?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 17, 2018, 04:18
Default Is this solution converged?
  #1
New Member
 
Michal Pacholczyk
Join Date: Sep 2016
Posts: 3
Rep Power: 5
michalpacholczyk is on a distinguished road
Hi

can you please help me to assess if this solution is converged?
This is simulation of wind tunnel nozzle. Boundary conditions as in given attachemtn? Can i consider this values of residuals as low enough since they are straight line? This is simulation with standard k-epsilon turbulance model.
Any ideas how to improve resiuadals? Do you think no slip wall outside of the nozzle is a good idea?
Attached Images
File Type: png contour.PNG (130.2 KB, 30 views)
File Type: png covergance.PNG (31.8 KB, 39 views)
michalpacholczyk is offline   Reply With Quote

Old   May 17, 2018, 10:27
Default
  #2
Member
 
Marcin
Join Date: Jun 2016
Posts: 77
Rep Power: 6
destroy is on a distinguished road
Cześć Michał,

There are several ways to assess convergence:
- the level of residuals (for example 1e-3 for continuity, 1e-6 for energy)
- mass and energy balance
- tracking some monitor plot, for example area-weighted average of pressure
destroy is offline   Reply With Quote

Old   May 17, 2018, 18:16
Default
  #3
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,007
Rep Power: 48
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
I would say they are.
1. Your contours look nice, meaning the initial condition seems to be gone.
2. Your residuals are flat/horizontal. Regardless of how high/low they are, the solution probably is not changing at all. Even if it is wrong or poor quality result, you probably cannot improve it anymore. I don't really care what is the magnitude unless it is 1000. But if it is 1e-03, 1e-05, does not make much difference. Anyway you know it will not go any lower than what it is.

If you are not convinced. It is a good idea to verify the flow hasn't changed. You can make the same contour screenshot at different iterations and visually inspect. More quantitatively you make a point monitor or line monitor or surface monitor and check the any or all of the pressure, temperature, velocity, and so on and verify that nothing changes.
LuckyTran is online now   Reply With Quote

Old   May 18, 2018, 05:26
Default
  #4
New Member
 
Michal Pacholczyk
Join Date: Sep 2016
Posts: 3
Rep Power: 5
michalpacholczyk is on a distinguished road
hi Guys,

thanks you so much for help - actually i have changed all oustide nozzle boundaries to pressoure outlet and it has resulted in pretty nice convergance (as attached). Right now i am sure my solution is quiet ok with Y+ at wall in bound 13-22.

thanks
Attached Images
File Type: png covergance2.PNG (36.6 KB, 26 views)
michalpacholczyk is offline   Reply With Quote

Old   May 18, 2018, 15:04
Default
  #5
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,007
Rep Power: 48
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
Looks nice.

# of cells with reversed flow not changing is also a reassuring indicator that the solution is converged (i.e. always 358 faces).
LuckyTran is online now   Reply With Quote

Reply

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
solution is converged but a problem flow_CH FLUENT 9 June 2, 2020 09:34
Restart (continue) converged solution from endpoint ISV Structural Mechanics 1 August 31, 2017 16:25
Why the solution could only be converged in aestas FLUENT 11 October 20, 2015 04:31
Solution not converged for supercritical annular flow K.Saikia FLUENT 0 November 14, 2014 02:29
solution is not getting converged Nijanthan FLUENT 5 July 25, 2013 01:42


All times are GMT -4. The time now is 19:24.