Learning Forum

[zoelle.wong]

Hello! I have quick clarifying questions about defining absorption coefficients as a material property and in the P1 or DO radiation physics modules: 

How is the absorption and scattering coefficient in the material property definitions different than the absorption coeffiicent that we would in the radiation module? 

How is the absorption and scattering coefficient that we specify as a material property used for solving the radiation transport equation? (Assuming we select a radiation model but don't provide absorption coefficients)

Thank you!

[zoelle.wong]

my mistake; I realize now that the absorption coefficient becomes enabled when you click a radiation model. That being said i have a follow-up question:

I'm interested in using the P1 Radiation model where I use a non-gray model. This requires a set number of bands and start/end wave numbers. In some of the papers I read, there is a way to specify a mean absorption coefficient that for a given range of wave number. In the material property database, how would users specify a mean absorption coefficinet for a given range of wave number? thanks!

[Rob]

You'd set the band absorption in the Materials panel. The database is best used once you set up manually to re-use the material elsewhere, but user-defined databases do have a few issues so make sure all models are ON before reading the database for your materials.  

[zoelle.wong]

to clarify - i don't see a way to specify the band absorption range in the materials panel (took a screen shot below); i see there's a way to specify the absorption coefficient as a function of temperature. Thank you!

[Rob]

Grey-band, not the most obvious setting! 

[zoelle.wong]

thank you! that was counter intuitive! Another follow up question (sorry for the spam!)

Is there a way to specify a set of abosrption coefficients (AC) for a given temperature? Or in other words, a gray model for a specific temperature? My sim has temperautres between 5-15 kK and the AC is are different for a given constant temperature, as seen from the bottom 2 screen shots below (from http://dx.doi.org/10.1615/HighTempMatProc.v10.i1.50). If a UDF is the only way to achieve this, where do you recommend that I start in the UDF manual? thank you again!

[Rob]

I think you can do that via DEFINE_GRAY_BAND_ABS_COEFF  https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v242/en/flu_udf/flu_udf_ModelSpecificDEFINE.html%23flu_udf_sec_define_gray_band_abs_coeff