radiation
Hi everyone,
I am using chtMultiRegionFoam in openFoam 2.0.1 my model has 4 parts inclouding 3 solid parts(glass, fiberglass (as insolation) , aluminum) and 1 fluid(air) part. in constant folder of solid parts we can see a solidThermophysicalProperties which have a radiation properties section similar to the following: //- radiation properties kappa kappa [0 -1 0 0 0 0 0] 0; sigmaS sigmaS [0 -1 0 0 0 0 0] 0; emissivity emissivity [0 0 0 0 0 0 0] .88; :confused: first question: as i have read sigmaS is Scatter coefficient [1/m] and kappa is Absorption coefficient [1/m]. is it true? what are these coefficients? absorption coefficient for solids should not be dimensionless? does scattering have any meaning for solids? :confused: second question: what are the values of absorption and emission coefficient for air in ordinary temperature? :rolleyes::) |
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Hi, Here is a very good link to understand the details of Radiation modelling from chalmers university. I hope it can be helpful to you.:) http://www.tfd.chalmers.se/~hani/kur...Foam_final.pdf |
Hi,
Thank you for the link , I had read it yesterday , before I made this thread, unfortunately it didn't answer my questions:( |
it is interesting, nobody knows!:(:(
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Absorption coefficient is a kind of decay length, hence the unit.
I don't know the absorption coefficient for air at room temperature, sorry. Keep in mind that in reality the absorption coefficient is a function of the frequency. In the case of a grey radiation model the absorption coefficient is spectrally averaged. I don't know much about the scattering coefficient, I don't use it for gases. It might be useful if the gases contain particles, maybe in flame simulation? |
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