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

DO Model giving wrong results for optically thick media ?

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 7, 2011, 09:58
Default DO Model giving wrong results for optically thick media ?
  #1
New Member
 
Salvatore Cunsolo
Join Date: Jan 2011
Posts: 2
Rep Power: 0
pprllo is on a distinguished road
First of all, hello everyone as this is my first post here !

Now, the problem.

I set up a very simple case, 2 walls at set temperature separated by a fluid. No gravity. No scattering.

Then i tried solving it:
- Without radiation
- With Rosseland radiation model.
- With P-1 radiation model.
- With DO radiation model.

Well, while Rosseland and P-1 results are consistent across a range of temperatures and absorption coefficient, I noticed that the wall fluxes calculated with the DO model are always higher than those calculated with Rosseland or P-1.

At this point i set the absorption coefficient at an extremely high value (10^9) and, while the Rosseland and P-1 models give me the predictable result (i.e. radiation heat transfer become negligible), the DO model still gives very high values of radiation heat transfer.

Any ideas ?
pprllo is offline   Reply With Quote

Old   January 11, 2011, 16:39
Default
  #2
New Member
 
Salvatore Cunsolo
Join Date: Jan 2011
Posts: 2
Rep Power: 0
pprllo is on a distinguished road
Upping the thread. Maybe someone has an idea.
pprllo is offline   Reply With Quote

Old   January 21, 2011, 13:45
Default
  #3
Member
 
Nikolopoulos Aristeidis
Join Date: Jan 2011
Location: Athens, Greece
Posts: 62
Rep Power: 15
Nikolopoulos is on a distinguished road
Which version of fluent are you using?
Nikolopoulos is offline   Reply With Quote

Old   April 16, 2013, 22:27
Default
  #4
New Member
 
gefei
Join Date: Apr 2013
Posts: 1
Rep Power: 0
i_flying is on a distinguished road
Quote:
Originally Posted by pprllo View Post
First of all, hello everyone as this is my first post here !

Now, the problem.

I set up a very simple case, 2 walls at set temperature separated by a fluid. No gravity. No scattering.

Then i tried solving it:
- Without radiation
- With Rosseland radiation model.
- With P-1 radiation model.
- With DO radiation model.

Well, while Rosseland and P-1 results are consistent across a range of temperatures and absorption coefficient, I noticed that the wall fluxes calculated with the DO model are always higher than those calculated with Rosseland or P-1.

At this point i set the absorption coefficient at an extremely high value (10^9) and, while the Rosseland and P-1 models give me the predictable result (i.e. radiation heat transfer become negligible), the DO model still gives very high values of radiation heat transfer.

Any ideas ?
I have get the same answer as you said, and when the optical thickness is very large, the convergence by do model with do/energy coupled is very fast , the P1 model is very low. which model you selected last?
i_flying is offline   Reply With Quote

Reply


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
Model of pump nonoptimal regimes get bad results Georg CFX 3 May 21, 2008 01:53
simulation results for k-w model and SST model Li CFX 7 June 29, 2007 05:19
multiphase model gives unreal results easycad FLUENT 14 April 17, 2005 08:52
standard k-eps model results? cfd Main CFD Forum 1 March 29, 2005 19:19
contradicting results of different turbulent model dani FLUENT 0 July 6, 2004 03:07


All times are GMT -4. The time now is 16:59.