Hi John,
This CFD “solver” is only a toy solver that we intend to use as a basis for a Julia lecture (just like I did with my toy 2D Shape collisionner Plot a circle with a given radius with Plots.jl - #8 by LaurentPlagne
https://discourse.julialang.org/uploads/short-url/tJmPIH9nmhtaudwxmZR8HexScwy.gif
I have translated the famous mit18086 from Matlab to Julia and replaced the cholmod solver by an home made geometric multigrid solver (that must be able to solve full neumann B.C.) translated from C++ to Jula.
The resulting Julia code is reasonably fast (5-100 times faster than the matlab original code depending on the mesh size)
For your question, I dot not use the classical post-processing workflow and the Makie plots are computed and displayed during the simulation (and the movie being recorded live) but I do not emit a frame by timestep: there is about 20k \Delta t and around 200 frames 
I agree that visualization during simulation is rather convenient and do this only with Julia is very nice !