Material properties:absoption and scattering coeff

Novice

Hi all,

I am simulating the radiation of a UV lamp inside a cylindrical volume(cylinder contains water) using Dicrete ordinates-non gray model. When I activate the DO model FLUENT is giving a message that the material properties have to be changed(and new propety fields like absorption coeff; scattering coeff appears in the materials panel). How to calculate the absoption and Scattering coefficients???

Please let me know the procedure how to calculate these coefficients.

Thanks in advance