I am fiddeling with a small program, called powder toy
Check out phun
It's even better and free...
well it was free now they changed the name to algoodo and it is no longer free
Free versions are still available though...
unfortunatelly you can't model gases with them (and probably neither algoodo can)
However, you can model gases by creating a bunch of tiny particles
JSR, now you can get your overcomplicated designs to cycle