[mooving]

hello.
i'm working on a simulation about gas flow.
as the pictures i attached
i wanna make an animation that i can see the flow of gas.
in the pictures i attached, we can see the diffusion not based on some surface, but on meshes in 3d.
i knew how to do it, but i completely forgot how to do it.
how can i do it?
i guess i have to use contour, but i don't know further...

[mooving]

i think my pictures aren't attached...