combustion, solution problem

Whitebear · April 15, 2014, 01:47

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!

bharath · April 15, 2014, 02:48

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.

Whitebear · April 15, 2014, 04:48

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.

ghorrocks · April 15, 2014, 05:43

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.

Whitebear · April 17, 2014, 05:11

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?

ghorrocks · April 17, 2014, 21:55

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.

Whitebear · April 18, 2014, 03:43

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.

April 15, 2014, 01:47	combustion, solution problem	#1
Whitebear Member Jinwhan Ryuk Join Date: Feb 2013 Location: South Korea Posts: 91 Rep Power: 13	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!

April 17, 2014, 05:11	Coal combustion tutorial radiation setup	#5
Whitebear Member Jinwhan Ryuk Join Date: Feb 2013 Location: South Korea Posts: 91 Rep Power: 13	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?

April 18, 2014, 03:43	I found some clue.	#7
Whitebear Member Jinwhan Ryuk Join Date: Feb 2013 Location: South Korea Posts: 91 Rep Power: 13	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.

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April 15, 2014, 02:48		#2
bharath Senior Member Bharath kumar Join Date: Apr 2009 Posts: 169 Rep Power: 17	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.

April 15, 2014, 04:48		#3
Whitebear Member Jinwhan Ryuk Join Date: Feb 2013 Location: South Korea Posts: 91 Rep Power: 13	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.

April 15, 2014, 05:43		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	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.

April 17, 2014, 21:55		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	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.