I'm not an expert in the field, but I've found Butterfly, from Ladybug tools as a very good introductory point to the vast world of CFD. It is opensource, and runs over Rhinoceros+Grasshopper, linking your geometry to the well-known engine, OPENFOAM. Even more importantly for this initial stages is the active online community backing it up.
Other commercial options would be ANSYS or Autodesk CFD, it all depends on your budget, timing to get it up to speed and project requirements.
As Dave mentions, then you have DesignBuilder integrated CFD module, that I find quite limited, or an even simpler one, Autodesk Flow Design. Again, it all depends on your needs.