I'd really like to know what I should change, to alter the divergence behaviour of my sim. As far as I can tell the current sparse set up in pyro (without flames, only smoke) is divergence free, right?

This doesn't seem right since air is compressible. Especially hot air should also try to expand slightly and push areas. In my current sim, mostly the basic setup, I have a high temperature cloud moving up (like the usual mushroom cloud).

What I miss is that the smoke beneath the rising plume gets advected. The hot air is constantly rushing up, but it's outer shell remains pretty steady. Shouldn't the hot upstream of hot air advect the colder outer air and pull it up also? Thought viscosity could help slightly, but it's not really working. My smoke emitter is quite large (50m diameter). Some stuff looks really nice, but then the way the “older” smoke behaves is too steady.

Anybody some ideas? Is the non divergent multigrid responsible for it? Or the pressure field? And what do I need to alter to make it behave like real air/gas that can change its volume?

Cheers
Tom

just create and source in a @divergence volume.