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February 4, 2014, 10:56 
buoyantSimpleRadiationFoam is missing in OF v2.2.2

#1 
Senior Member
Yuehan
Join Date: Nov 2012
Posts: 131
Rep Power: 7 
Hi Foamers,
I found the solver buoyantSimpleRadiationFoam missing in the latest OF version 2.2.2. Does anybody know what happend and why? Thank you. 

February 5, 2014, 03:17 

#2 
Senior Member

Hi,
Radiation is now automatically included in the heat transfer solvers. So you can use buoyantSimpleFoam and choose a radiation model there. If you want to solve without radiation just use the 'none' model. Regards, Tom 

February 6, 2014, 15:59 

#3  
Senior Member
Yuehan
Join Date: Nov 2012
Posts: 131
Rep Power: 7 
Quote:
Thank you Tom. I am still wondering why radiation is not included in buoyantBoussinessqSimpleFoam? If I want to simulate natural convection, how can I include the effect of radiation if I don't to want to use buoyantSimpleFoam? [...] I am wondering the reason why why radiation is not included in buoyantBoussinessqSimpleFoam. If I want to simulate a natural convection, how can I include radiation if I don't use buoyantSimpleFoam? Thank everybody! Last edited by wyldckat; February 6, 2014 at 18:18. Reason: merged two posts, since they were posted 2 minutes apart 

February 6, 2014, 18:39 

#4 
Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,130
Blog Entries: 39
Rep Power: 110 
Greetings to all!
I don't know for certain, but it's possible that the radiation model might not be implemented in OpenFOAM 2.2 either because:
Anyway, I spotted the other day that Symscape's patches for their port of OpenFOAM 2.2.x for Windows: http://www.symscape.com/openfoam22xonwindows  have got the aforementioned radiation model implemented in the solver buoyantBoussinesqSimpleFoam. Attached is an excerpt of their patches, which only has the patch for the solver alone. To use it, follow these steps:
Best regards, Bruno
__________________
Last edited by wyldckat; February 6, 2014 at 18:39. Reason: had forgotten to attach the file 

February 7, 2014, 03:25 

#5 
Senior Member

Hi,
My guess would be that radiation with Boussinesq assumption would be rarely valid. Since for radiation to be important you need large temperature differences, which makes the Boussinesq approach inaccurate. Also the radiation models result in an energy source and not in a temperature source, while buoyantSimpleFoam solvers for energy or enthalpy and buoyantBoussinesqSimpleFoam solves for temperature. I guess there is some programming needed to combine everything like Bruno pointed out. Regards, Tom 

February 10, 2014, 15:39 

#6  
Senior Member
Chris Sideroff
Join Date: Mar 2009
Location: Ottawa, ON, CAN
Posts: 407
Rep Power: 15 
Simply saying large temperature differences for radiation can be misleading and there are radiation cases where the Boussinesq approximation is valid.
To demonstrate, one can use the following equations to estimate the magnitude of radiation's contribution to the heat transfer versus convection: Now compare temperature difference versus heat flux for both. You'll find the relative contributions depend on , for convection, and , for radiation. See the plot I quickly threw together where I plot for two values of and for two values of . (note: in the legend I used Celsius but I did the calculation with Kelvin.) For small values of or large values of their relative magnitudes are close. So relative to convection, the importance of radiation depends on the convective heat transfer coefficient, the absolute level of temperature or both. Even though the Boussinesq is valid for there are situations where it's valid to use it with radiation (left half of the plot). My point is the importance of radiation is a little more complicated than simply saying only for large temperature differences. Additionally, radiation can be important for heat transfer problems even if the radiative contribution from the gas is negligible. Chris Quote:
Last edited by cnsidero; February 11, 2014 at 09:39. 

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