Defining an Abstract base class using Python's abc module
Abstract classes are an excellent way to help your development team and your personal code base stay within constraints and required implementations. I was going to write up something of my own about this for helping train new technical artists, but this covers it well!
Compressible and in-compressible Naiver-Stokes Fluid dynamic equations
I first learned about Naiver-Stokes equations when reviewing Bifrost for Maya. I'm no mathematician, but I found this site explained the equations extremely well! For practical use in CG, Bifrost excludes compression from it's evaluation, but this page should help explain the math behind the nodes!