CFD Online Discussion Forums

CFD Online Discussion Forums (
-   CFX (
-   -   combustion, solution problem (

Whitebear April 15, 2014 01:47

combustion, solution problem
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!:confused:

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

Coal combustion tutorial radiation setup
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

I found some clue.
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. :)

All times are GMT -4. The time now is 13:52.