Since moving obstacles are not supported by the Blender 2.5 Smoke Sim right now I tried to use a moving force field instead. At first glance it seemed to work, but after passing the smoke some sort of vortex opened. Very weird behaviour:
Could you post a blend file? I think it looks pretty cool, actually! But it’s hard to tell what it’s supposed to do without seeing how the fields are placed, etc.
It looks like the field you used was puffing the smoke away but only in an instance, you can see the tail of the smoke pass through the centre unhindered.
Thanks for offering help - here is the .blend: http://www.********.org/blend/3727
It’s just a spherical forcefield passing through the smoke. Until 00:04 everything works fine, then the weird behaivour sets in. Looks like some sort of backfire…
Edit: What’s wrong with links to paste all? Is it a scam?
http://raubkopictures.de/files/forceobstacletest.blend
I wonder if that bit of weirdness is happening because the force field passes outside of the domain – as if its forces were bouncing off the domain wall or something. I animated the force field’s STRENGTH parameter from 1000 to 0 right after if passed through the smoke (I animated it between frames 115 and 116 e.g.). That might create the results you’re after. Of course that doesn’t necessarily explain why it was behaving the way it did…
PS: 196 divisions… showoff… 
Did you bake it at 196 divisions? Because said behaviour does not happen when using 128 or less divisions…
I’m on a mac with 12GB RAM. 196 crashed Blender for me. I think I ran the sim at 48.
Wow, I baked it on a Mac with 4 GB RAM…
I’m running 10.6.2 – what are you using?
10.5.8 - I’m using the 64bit build of Blender