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

combustion, solution problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 15, 2014, 01:47
Default combustion, solution problem
  #1
Member
 
Jinwhan Ryuk
Join Date: Feb 2013
Location: South Korea
Posts: 54
Rep Power: 4
Whitebear is on a distinguished road
Does anyone have blinking problem while the problem is solving? I am solving coal combustion problem and it has 1 million nodes size. Once I start parallel running then solver is running and then Out file screen go upward and dowward for a long time at 1st iteration and then move to 2nd iteration. 2nd iteration also shows the same phenomena. One iteration takes about 40 minutes. Please help me!
Whitebear is offline   Reply With Quote

Old   April 15, 2014, 02:48
Default
  #2
Senior Member
 
Bharath kumar
Join Date: Apr 2009
Posts: 157
Rep Power: 8
bharath is on a distinguished road
I think this is memory problem.

What is your system configuration?Combustion will take more time to solve.

Reduce your mesh size and try again.
bharath is offline   Reply With Quote

Old   April 15, 2014, 04:48
Default
  #3
Member
 
Jinwhan Ryuk
Join Date: Feb 2013
Location: South Korea
Posts: 54
Rep Power: 4
Whitebear is on a distinguished road
Thank you very much for your fast reply. I am using 64gigabite memory. According to windows manager, 10.6GB meories are used. The problem is that CPU. CPU shows only 1% usage and suddenly goes up 90%. I also use SSD and Intel i7-4930K@3.40GHz CPU.1 million cell is not enough for my problem. This is the minimum number to avoid overflow calculation.
Whitebear is offline   Reply With Quote

Old   April 15, 2014, 05:43
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,672
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Something sounds seriously wrong with your simulation. You probably have a poorly set up physical model. Are you using radiation modelling? A poorly set up radiation model can do that sort of thing.
ghorrocks is online now   Reply With Quote

Old   April 17, 2014, 05:11
Default Coal combustion tutorial radiation setup
  #5
Member
 
Jinwhan Ryuk
Join Date: Feb 2013
Location: South Korea
Posts: 54
Rep Power: 4
Whitebear is on a distinguished road
Thank you very much for your reply. Thermal Radiation: Discrete Transfer, Number of Rays:32, Emissivity: 1, Target Coarsening Rate: 16, some walls emissivity: 0.6 I just followed coal combustion tutorial setup. Is it so sensitive that show such a problem? Could you tell me how to fix this? 24 iterations take 48hours now...I tried number of rays and emmisivity but it didn't help. As far as I know Discrete Transfer model is the only one that can adapt coal combustion problem, isn't it? What kind of radiation solving options which I can chose?
Whitebear is offline   Reply With Quote

Old   April 17, 2014, 21:55
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,672
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Well, the radiation model is the problem. You may need some serious CPU time on the radiation model - that depends on the detail of what you are modelling.

I recommend you start with a simple model where you have a known answer to reproduce and check the radiation model is behaving as expected. Only once you have a good feel for the radiation model should you attempt the large complex model.
ghorrocks is online now   Reply With Quote

Old   April 18, 2014, 03:43
Default I found some clue.
  #7
Member
 
Jinwhan Ryuk
Join Date: Feb 2013
Location: South Korea
Posts: 54
Rep Power: 4
Whitebear is on a distinguished road
Thank you very much for your help. You are definately right! I put inapropriate options in radiation setup. I look over my model again and change some variables. It works now.
Whitebear is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Future CFD Research Jas Main CFD Forum 10 March 30, 2013 13:26
Problem using EDM for combustion nakul FLUENT 1 August 11, 2011 05:01
combustion problem mcnair CFX 0 March 27, 2011 23:42
Combustion problem in STAR CD... help me, please! mrkokoko STAR-CD 1 September 14, 2009 17:00
injection in Combustion problem CCS FLUENT 2 November 21, 2003 10:20


All times are GMT -4. The time now is 03:20.