Governing equation behind the simualtion

How can I see the governing equation that is used behind the simulation?
is it available in the MFix manual?
I want see the mass, momentum, energy, and constitutive equation Kinetic theory of granular flow (KTGF) equation. please let me know.

Ultimately, the source code is the definitive source of information. “Use the source, Luke”, as they say.
But there are some manuals which may help - have a look at the “Summary of MFiX Equations” and “Theory Guide” available at
But be advised that these documents are a bit old and some things may have changed since they were written.