Hi, I'm trying to write UDF for heat flux at the wall. The heat flux is a function of concentration of water.

qid = 1234 * species_water

And I have a problem of how to get the source variable of water species (species_water above). It seems that I can use variables of cid, cir but none of them is for species. Please help me in this.

Try the variable C_YI(cell,thread,species) where the species index is that for water in your list. C_YI should be the mass fraction.

Thank you for your help. I wonder if there is any index for the terms such as temperature, species, etc..