energy balance

zdz198728 · November 18, 2009, 22:49

Hi, guys:
I am doing a combustion case with PDF model. I have opened the P1 radiation model. However, the energy balance are not good? I am not sure what the problem is. Is radiation is main reason of this problem? How could we get energy balance.

Thanks

Charles Rundle · November 19, 2009, 00:07

Hello,

I haven't worked with combustion to any extend to please take my advice from that perspective. It has also been awhile since I've used the P1 radiation model.

If I may ask, are you determining your energy balance based on a report provided at the end of the solver run or by comparing the energy flows in the post data? Also are you performing a transient or steady state analysis? If nothing else I would recommend checking to make sure the method you are using to determine the energy balance is correct. I would pay special attention to make sure that no energy sources have been left out.

If the method being used is correct I have a few suggestions. In the past I've found that sometimes a higher level of convergence is required to get good energy balance. Perhaps let it converge to a RMS value one magnitude lower to see it improves the energy balance. If I recall correctly, I'm away from my computer with the documentation on it, the P1 model works with rays, increasing the number of rays may improve you energy balance as well, although at the cost of computational effort.

I may also be linked directly to the fact this is a combustion problem in which case I'm afraid I'm out of my depth.

I hope I have been helpful. Have a good day.

CAR

November 18, 2009, 22:49	energy balance	#1
zdz198728 New Member Dezhi Zheng Join Date: Sep 2009 Posts: 8 Rep Power: 16	Hi, guys: I am doing a combustion case with PDF model. I have opened the P1 radiation model. However, the energy balance are not good? I am not sure what the problem is. Is radiation is main reason of this problem? How could we get energy balance. Thanks

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November 19, 2009, 00:07		#2
Charles Rundle New Member Charles Rundle Join Date: Oct 2009 Posts: 9 Rep Power: 16	Hello, I haven't worked with combustion to any extend to please take my advice from that perspective. It has also been awhile since I've used the P1 radiation model. If I may ask, are you determining your energy balance based on a report provided at the end of the solver run or by comparing the energy flows in the post data? Also are you performing a transient or steady state analysis? If nothing else I would recommend checking to make sure the method you are using to determine the energy balance is correct. I would pay special attention to make sure that no energy sources have been left out. If the method being used is correct I have a few suggestions. In the past I've found that sometimes a higher level of convergence is required to get good energy balance. Perhaps let it converge to a RMS value one magnitude lower to see it improves the energy balance. If I recall correctly, I'm away from my computer with the documentation on it, the P1 model works with rays, increasing the number of rays may improve you energy balance as well, although at the cost of computational effort. I may also be linked directly to the fact this is a combustion problem in which case I'm afraid I'm out of my depth. I hope I have been helpful. Have a good day. CAR