Is this like a ball check valve? There used to be a tutorial (very simple 2D, but the thought process was excellent). If you are not expected to have any deformation in the solid body or are not interested in the stresses of the object, then you can leave the Mechanical part out and simply conduct the simulation in CFX or Fluent. There is also the 6DOF solver in Fluent that you may want to consider. Going to Rocky may be good if you had a large number of objects, but it seems like you only have one.