Federico Alzamora Previtali

Hello Milne, 

since your pendulum undergoes 1DOF rotation about the X-axis, you will need to enter the Ixx moment of inertia passing through the center of mass. Specifying the center of rotation and axis in the 6-DOF Properties dialog box, and the center of gravity location in the Dynamic Mesh Zones dialog box, Fluent will compute the correct moment of inertia during calculation.

I hope this helps.