I’m very happy to hear that our most recent update has been helpful to you.
Regarding your question: Generally speaking, the mass exchange is used for the calculations of interface cells that are found between liquid and gas cells (see e.g. Thürey, Nils, C. Körner, and U. Rüde. “Interactive free surface fluids with the lattice Boltzmann method.” Technical Report05-4. University of Erlangen-Nuremberg, Germany (2005)).
The exact details, however, are too complex to elaborate on here: We are always open to the possibility of providing further support within a joint collaboration project.
I hope you all the best in your research.