How to modify the interfacial reflectivity at semi-transparent walls for DO model
When using the discrete ordinates (DO) radiation model, there are situations when an user wants to modify the interfacial reflectivity at diffusely reflecting semi-transparent walls computed by FLUENT based on the refractive index of the medium.
You can use the DEFINE_DOM_DIFFUSE_REFLECTIVITY macro when you want to modify the interfacial reflectivity at diffusely reflecting semi-tranparent walls computed by FLUENT based on the refractive index values of the medium. During the Fluent execution, the same UDF is called for all the semi-tranparent walls, so the DEFINE_DOM_DIFFUSE_REFLECTIVITY macro can be used to modify diffuse reflectivity and diffuse transmissivity values at the interface.
Macro: DEFINE_DOM_DIFFUSE_REFLECTIVITY(name, t, nband, n_a, n_b, diff_ref_a, diff_tran_b, diff_ref_b, diff_tran_b)
Function returns: void
There are 8 arguments to DEFINE_DOM_DIFFUSE_REFLECTIVITY: name, t, nband, n_a, n_b, diff_ref_a, diff_tran_a, diff_ref_b, diff_tran_b. name is the name of the UDF, defined by you. Once you have compiled and linked the UDF, the name you have chosen for your function will become visible and selectable in the graphical user interface in FLUENT. t, nband, n_a, n_b, diff_ref_a, diff_tran_a, diff_ref_b, diff_tran_b are variables that are passed by the FLUENT solver to your UDF.
t is a pointer to the thread. The band number is represented by nband. This argument is needed for non-gray DO model. n_a and n_b represents the refractive indexes of medium a and b. diff_ref_a and diff_tran_a are the diffuse reflectivity and diffuse transmissivity, resepctively, at the interface facing medium a. Similarily, diff_ref_b and diff_tran_b are the diffuse reflectivity and diffuse transmissivity, respectively, at the interface facing medium b.
DEFINE_DOM_DIFFUSE_REFLECTIVITY is called by FLUENT for each semi-tranparent walls and also for each band (in case of non-gray DO model).