Can there be applications of graph theory, combinatorics etc. in PDEs mainly hydrodynamics?

Tried my luck with Google's search engine, didn't show much info. I guess you can try to use these features of GT and combinatorics in QFT (there's a section in Kaku's book on QFT on forests and skeletons from GT).

And what sort of applications are there?

I am asking, since I am thinking of taking courses in infinite combinatorics, axiomatic set theory and forcing this coming semester, and would like to know if it's not redundant. (As someone who likes to learn a lot it won't be redundant, but I guess I am asking would it have applications to PDE in Hydrodynamics).

I once in my search found a book on categories in continuum mechanics by Lawvere, so perhaps there are such attempts to use algebra and combinatorics in analysis. https://link.springer.com/book/10.1007/BFb0076928