The main features of CellFlow are:
-Freeware open source (Download VB6 source code)
-It can do any number of dimensions: 1, 2 and 3 dimensions, but also (just for fun) 4 and higher.
-It does an animation as it calculates.
-It works as a dynamical direct numerical simulation: With compressible flow, in explicit time dependence.
-Input files generated by a spreadsheet.
-Models pressures, flows, temperatures, and chemical species.
-Also suitable for acoustic simulation, and for simulation of aero acoustics (eg whistles)
To be fair, I can think of a few drawbacks:
-Only (topologically) rectangular grids. But cells need not be equal in size.
-No implicit turbulence model is implemented. But if you use a fine enough grid, you get turbulence explicitly.
Both of these drawbacks can of course be addressed. Maybe I will work on it if I have time.
Here are some pictures I generated for a ball in a channel, in 2D, 3D, and 4D.
2D, 3D and 4D velocity plots for an n-dimensional ball in a channel.
For 2D, this gives the well known "von Karman vortex street".
The 3D and 4D pictures are of course cross sections.