Autodesk Project Falcon is a technology preview of wind tunnel simulation software that is free to download from Autodesk Labs. It is branded, not surprisingly, at the manufacturing and product design areas but I have been looking at this for early conceptual studies on unusual structural shapes to help understand the effects of wind speed, eddies and implied wind pressures.
The best thing about project Falcon is the ease of use, open it up, import an STL file and use the on screen tools to set wind direction, speed and wind axis. You will then see a conceptual 2D analysis as shown above on my conceptual structure. You can then move the 2D plane across the structure to study wind speeds and pressures at different locations around the structure. If you have time, you can set Falcon to show flow lines using the 3D simulation which takes into account the whole shape rather that a 2D slice. I first tested the tool out on a number of simple shapes just to get an understanding of how the software works. I created the shapes in AutoCAD using solids and then created STL files by typing STLOUT at the command prompt.
You can take models directly from Revit if you have the STL output loaded or save as an ACIS solid and then open in AutoCAD.
Anyway, if you have time I urge you to take a look at this. Apart from being really good fun it may help Engineers understand the way pressures can build up around complex shapes on structures.