PFlow motion to smoke after creation

[mark_aldred]

I have a PFlow system that's orbitting around a centre point. I'm using the particles as a source and cutting off the smoke creation (surface force) after all the particles have made about one orbit to give me a disk of gas. What I'd like to do is have the smoke follow the motion of the particles after that too. How can I do it? The Motion Velocity checkbox doesn't seem to be having any effect.

Thanks