While 3D computer graphic animations are generally controlled "by hand," meticulously and deliberately planned, 3D simulations are governed more by thoroughly "automatic" forces. Virtually every physical force and substance you can think of, such as wind, gravity, fluids, gases, and combustion, can be simulated mathematically.
Simulations can be beautiful to look at, done right, but they can still be excruciating to set up, control, and edit, even though the computer does a lot of the work. The software is also always changing, a double-edged sword of ever-evolving interfaces and incrementally easier set-up options.
The following are a few of my attempts to learn and test liquid and combustion simulations, and to apply them to client projects.