KNOWN ISSUE: For multiphase Fluent cases, 'Velocity' is not the relative velocity in CFD-Post
For results from a multiphase, multiple frame of reference simulation in Fluent, the variable named 'Velocity' is the velocity relative to the stationary frame, and not the velocity relative to the rotating frame, as it should be.
There is a coding error in the way CFD-Post calculates the relative velocity.
Construct a new variable subtracting the frame velocity from the fluid velocity.
ANSYS CFX Release 12.1.