sci.physics.computational.fluid-dynamics

Hello,

I'm searching for a software(open source or free) to simulate an
object, which can rotate freely in all spatial directions. Its
rotation, which induces the movement of the fluid around it, is also
influenced/induced by the flow around it. Furthermore I need to
include gravity.

Does anybody have an idea which software I could use or any
suggestions how I can realize this?

Thanks,
Vera