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

Is the convergence of solution ok?

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

Like Tree2Likes
  • 1 Post By Achin
  • 1 Post By Achin

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 1, 2015, 16:57
Default Is the convergence of solution ok?
  #1
Senior Member
 
Aja
Join Date: Nov 2013
Location: Iran
Posts: 492
Rep Power: 10
aja1345 is on a distinguished road
Hi,

I am simulating an by using Fluent. The convergence of solution is monitored by checking the residuals of the numerically solved governing equations. Moreover, in order to judge the convergence, the behaviour of other quantities, such as the total pressure at the inlet and outlet boundaries, and torque coefficient generated by the rotor, are also monitored. Here, the default convergence criterion of each residual is reduced in order to allow the monitored quantities to stagnate at consistent values.

Now, according the following figures, Is the convergence of solution ok? and particularly about residuals?



















Last edited by aja1345; November 13, 2015 at 09:49.
aja1345 is offline   Reply With Quote

Old   November 2, 2015, 06:08
Default
  #2
New Member
 
Join Date: Nov 2010
Posts: 17
Rep Power: 11
Achin is on a distinguished road
I am unable to see your images. But I can suggest that don't just go by the scaled residuals. Other than that, it is also important to check the flux imbalance. Go to Reports and Fluxes. For convergence, the imbalance in fluxes should be less than 0.2% of the net flux through the domain.
aja1345 likes this.
Achin is offline   Reply With Quote

Old   November 2, 2015, 06:34
Default
  #3
Senior Member
 
Aja
Join Date: Nov 2013
Location: Iran
Posts: 492
Rep Power: 10
aja1345 is on a distinguished road
Quote:
Originally Posted by Achin View Post
I am unable to see your images. But I can suggest that don't just go by the scaled residuals. Other than that, it is also important to check the flux imbalance. Go to Reports and Fluxes. For convergence, the imbalance in fluxes should be less than 0.2% of the net flux through the domain.
Thanks for yours answer,

First, My English language is not good.

I will correct these figure.

some questions:

Therefore,according to your statement, one of convergence considerations is, checking mass imbalance. in other words, i should check this until i understand that solution converge or not. Am I right?

According to the following link, i understood that mass imbalance is equal to absolute value of (inlet mass-outlet mass). but How mass imbalance is computed as a percentage?

http://www.cfd-online.com/Forums/flu...tml#post571301
aja1345 is offline   Reply With Quote

Old   November 2, 2015, 06:39
Default
  #4
Senior Member
 
Aja
Join Date: Nov 2013
Location: Iran
Posts: 492
Rep Power: 10
aja1345 is on a distinguished road
Other figures:
aja1345 is offline   Reply With Quote

Old   November 2, 2015, 07:40
Default
  #5
Senior Member
 
Aja
Join Date: Nov 2013
Location: Iran
Posts: 492
Rep Power: 10
aja1345 is on a distinguished road
According to the following figure, Is this such scaled residuals logical?
Attached Images
File Type: jpg Capture4444.jpg (122.2 KB, 6 views)
aja1345 is offline   Reply With Quote

Old   November 3, 2015, 02:06
Default
  #6
New Member
 
Join Date: Nov 2010
Posts: 17
Rep Power: 11
Achin is on a distinguished road
Fluxes reported are with signed conventions. So you don't have to do any subtraction. Just note the "Net Results" which is your imbalance. It takes care of how much flux comes in (+ve flux) and how much is going out( -ve flux).
Then to calculate percentage: ( (Net Result)/(Inlet Flux) ) *100 should give you the percentage imbalance and it should be less 0.2.
aja1345 likes this.
Achin is offline   Reply With Quote

Old   November 4, 2015, 03:50
Default
  #7
Senior Member
 
Aja
Join Date: Nov 2013
Location: Iran
Posts: 492
Rep Power: 10
aja1345 is on a distinguished road
Quote:
Originally Posted by Achin View Post
Fluxes reported are with signed conventions. So you don't have to do any subtraction. Just note the "Net Results" which is your imbalance. It takes care of how much flux comes in (+ve flux) and how much is going out( -ve flux).
Then to calculate percentage: ( (Net Result)/(Inlet Flux) ) *100 should give you the percentage imbalance and it should be less 0.2.
Thanks.

Why do you say that it should be less 0.2?

Do you can present a paper and link about this value?
aja1345 is offline   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
In the case of convergence aja1345 FLUENT 1 July 31, 2015 04:58
Continuity Convergence Problem in CFX cfd seeker CFX 2 July 2, 2015 12:12
Solution Convergence Vignesh V OpenFOAM Running, Solving & CFD 1 July 15, 2012 12:31
solution convergence problem anbuselvan FLUENT 1 January 18, 2009 05:00
CFL Condition Matt Umbel Main CFD Forum 14 January 12, 2001 15:34


All times are GMT -4. The time now is 07:58.