Modeling of hopper flow

I am relatively new to yade. I am trying to model Hopper flow in yade. There are some few initial questions:
Is it possible to import CAD models in yade? I was planning to build the geometry of hopper in CAD and then import them in yade.
Once, i have the geometry, i would want to fill it with around 1 million particles. The hopper is approximately 6 ft high and has spheres with diameter ranging between 5mm - 12mm.
Next, i would like to observe the flow of the particles due to gravity.
How should i go about addressing this problem in yade?

-Shailesh