# P1 radiation model and 2D calculation

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 November 4, 2009, 02:00 P1 radiation model and 2D calculation #1 New Member   Xinyuan FAN Join Date: Sep 2009 Location: Beijing Posts: 13 Rep Power: 10 Hello, everyone! Can P1 radiation model be used to solve a 2D case? I want to calculating radiation using a 2D case. The case have front and back patches which are set to empty. But when solving the radiation equation (seems G equation of P1 model), it has an error called "Floating point exception". Can anyone tell me what the problem is? If I want to use P1 radiation model to solve a 2D case, what kind of boundary condition to use for front and back patches of G? Thanks.

 November 4, 2009, 02:40 #2 New Member   Xinyuan FAN Join Date: Sep 2009 Location: Beijing Posts: 13 Rep Power: 10 Sorry, it is my fault. The P1 model can be used to solve a 2D case. But it seems that in radiationProperties file, when using P1 model absorption coefficient and scatter coefficient can not be 0 at the same time. Is that true? Hope somebody can tell me the answer. Thanks.

 November 4, 2009, 05:24 #3 Senior Member   Aram Amouzandeh Join Date: Mar 2009 Location: Vienna, Vienna, Austria Posts: 186 Rep Power: 10 Hi Xinyuan, P1 radiation model can be used in 2D and also absorption and emission coefficients, a and e respectively, can be set to "0" at the same time, representing a (to radiation) non-participating medium. But I also experienced the crash of the solver (buoyantSimpleRadiationFoam with P1) when I set the values for a and e to "0". I solved the problem by entering a very small number like "1e-10" yielding reasonable results. Hope that helps! Cheers, Aram

 November 4, 2009, 22:53 #4 New Member   Xinyuan FAN Join Date: Sep 2009 Location: Beijing Posts: 13 Rep Power: 10 Hi, Aram Thanks for your reply. What you've said helps me a lot. Actually I am considering a non-participating medium in my case, so I think I can set a very small number to a just like you've done. Thanks again for your information. Xinyuan

 November 11, 2009, 03:03 #5 New Member   Xinyuan FAN Join Date: Sep 2009 Location: Beijing Posts: 13 Rep Power: 10 Hi, Aram I have another problem. If I set 1e-5 to a and 0 to e, I found there is no difference between results of P1 model and no radiation model. Seems that P1 model is applied more situations where the optical thickness is large. If I considers no participating media, should I use fvDom model instead of P1？I need your advices. Thanks in advance. Xinyuan

 November 11, 2009, 03:28 #6 Senior Member   Aram Amouzandeh Join Date: Mar 2009 Location: Vienna, Vienna, Austria Posts: 186 Rep Power: 10 Hi Xinyuan, try to set both coefficients, a and e, to 1e-5 or even smaller. Its interesting as I obtained reasonable results with P1 and a non-participating medium (for the case of two parallel walls T1, T2, T1

 November 11, 2009, 03:52 #7 New Member   Xinyuan FAN Join Date: Sep 2009 Location: Beijing Posts: 13 Rep Power: 10 Hi,Aram Thanks for your reply, I will have a try again. Xinyuan

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