I needed a simple fluid solver written in lua for a game jam, so I converted the solver from 'Real-Time Fluid Dynamics for Games' by Jos Stam.
The original paper that I got it from is here: http://www.dgp.toronto.edu/people/stam/reality/Research/pdf/GDC03.pdf
Included in this repo is an example of how to use it in Love2D, just run love from the folder to try it out.