CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Convergence in Free convection

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 4, 2013, 20:02
Default Convergence in Free convection
  #1
New Member
 
Join Date: Oct 2011
Posts: 19
Rep Power: 14
myty is on a distinguished road
Hi all,
I am new user of ANSYS/FLUENT 14.0, sometime i am running simulation of natural convection with boussinesq approximations for density, the simulations is going on with no error, residuals decreases rapidly at start and then constant. so i am confused that either i need to run for more iterations or it will not converge at all.
please guide
myty is offline   Reply With Quote

Old   May 5, 2013, 07:08
Default
  #2
Senior Member
 
ztdep's Avatar
 
p ding
Join Date: Mar 2009
Posts: 427
Rep Power: 19
ztdep is on a distinguished road
Send a message via Yahoo to ztdep Send a message via Skype™ to ztdep
Quote:
Originally Posted by myty View Post
Hi all,
I am new user of ANSYS/FLUENT 14.0, sometime i am running simulation of natural convection with boussinesq approximations for density, the simulations is going on with no error, residuals decreases rapidly at start and then constant. so i am confused that either i need to run for more iterations or it will not converge at all.
please guide
which level of does the residual decreases to.
could you pease upload your mesh system, and what is the Ra number.
ztdep is offline   Reply With Quote

Old   May 5, 2013, 13:00
Default
  #3
New Member
 
Join Date: Oct 2011
Posts: 19
Rep Power: 14
myty is on a distinguished road
All residuals decreases quickly to value close to convergence but then constant, means no further decrease. The mesh is simple rectangular box, with three walls adiabatic q''=0, and one side heating wall. Is there a role of Ra number to simulate natural convection. Also gravity value at -0.0098 gave convergence but when i increased it to -0.098 or -0.98, -9.8, situation is like i told.
myty is offline   Reply With Quote

Old   May 5, 2013, 21:04
Default
  #4
Senior Member
 
ztdep's Avatar
 
p ding
Join Date: Mar 2009
Posts: 427
Rep Power: 19
ztdep is on a distinguished road
Send a message via Yahoo to ztdep Send a message via Skype™ to ztdep
Quote:
Originally Posted by myty View Post
All residuals decreases quickly to value close to convergence but then constant, means no further decrease. The mesh is simple rectangular box, with three walls adiabatic q''=0, and one side heating wall. Is there a role of Ra number to simulate natural convection. Also gravity value at -0.0098 gave convergence but when i increased it to -0.098 or -0.98, -9.8, situation is like i told.
I high Ra number means a convection intensity, i strongly suggest you to increase the mesh density as the increases of Ra number(increases of gravity).
ztdep is offline   Reply With Quote

Old   May 6, 2013, 18:22
Default
  #5
New Member
 
Join Date: Oct 2011
Posts: 19
Rep Power: 14
myty is on a distinguished road
Thanks, i decreased the mesh size and now its working, one more thing is that when i am using velocity inlet BC for natural convection flow with very small value 10^-m/s, its working but when i am using pressure inlet BC which is preferred with natural convection flow, its not converging with constant wall T & q''. Do u suggest me something to run it.
myty 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
Free convection from vertical cylinder Mariusz FLUENT 1 February 2, 2017 14:36
Force can not converge colopolo CFX 13 October 4, 2011 23:03
Free convection BCs Craig Hildreth CFX 1 February 24, 2008 17:45
Free convection flow over vertical flat plate Polly Main CFD Forum 1 February 11, 2003 14:25
Composition driven free convection P.Fonteijn CFX 0 May 7, 2001 19:12


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