I am looking for CFD software that can help me analyze a gas regulator. I want to predict condensation and freezing buildups during intermittent flow, as well as model mechanical fluttering of the valves.

Do you know of any good multi-physics packages capable of doing this?

From the private responses I'm getting it would seem possible to model the icing/condensing problem, for instance the icing of aircraft wings. The flutter problem would seem to be tricky, requiring re-gridding of the domain for each time step.

There are codes that can apparently do all this, with perhaps minor programming effort to refine them. The short list includes CFX-4, TASCflow, Spectrum, PHOENICS, STAR-CD, RADIOSS and FLUENT. I have only seen results for TASCflow so far and only for a steady state condition.

Thanks for the encouragement of those who responded.

Thanks for posting this! It confirms what I've suspected - that there is a considerable amount of hidden traffic here. It's a pity since no one else can benefit from the answers given and independent observers can't protest if someone gives you false or very colored information.

Summarizing the answers like you did is great! Gives us other a chance to learn from your question also.