I have a smoke emitter that is under a rocket (but not touching anything). It emits smoke, but the smoke just sits there in a bubble. It doesn't flow. If I move the emitter away from the collision objects, it works fine. It's like the smoke won't get within a meter of any collision object, and this is a threshold that I can't seem to edit. Any ideas?
One problem could be the Resolution of the smoke domain as smoke will not enter a 'cell' that overlaps the obstacle. This is illustrated by the following image :
This is using a Smoke Domain Resolution of 64 - meaning that the 'cell' size is 1/64th of the longest X,Y,Z dimension of the smoke domain.
As you can see, the influence of the obstacle is 'stepped', clearly showing the individual grid cells. For 'flat' non-rotated surfaces this can be seen as a considerable gap between smoke and obstacle.
Choosing a much larger Resolution will reduce the size of the cells and the resulting in smoke that can get much closer to the obstacle.
Have you checked the boundaries of the Smoke Domain?
The Smoke Domain is a cube that determines the limits of the simulation of the smoke. It cannot escape it. The cube can be resized and it's shape changed, of course.