Modifying the energy equation in Fluent
I use non-premixed combustion model and I want to perform some changes in the diffusion term of the energy equation. I know that I have to use a UDF file to do that but I'm facing some difficulties in choosing the required macro to perform these changes. For example, if I write a UDF file using DEFINE_DIFFUSIVITY, Fluent will link this UDF to the UDS transport equation NOT the energy equation. So, Can you please give me some recommendations to modify the diffusion term (or any term) in the energy equation (or any equation) in terms of choosing the required macro.