Thank you for your reply.

I am modelling a fluid lubrication bearing system. For example a thrust bearing is consisted of a thrust disk and two layer of fluid lubricants. (see attached )The 2-way FSI simulations will calculate the forces generated by the fluid acting on the thrust disk in axial direction. The forces are passed to transient structure to get a displacement of the thrust bearing and then the displacement is passed to Fluent to update the fluid domain geometry using dynamic meshing(squeeze one of the fluid domain and expand the other) . So for a thrust bearing, there are two fluid film warp the disk like a sandwich. But these two fluid domain are operating in exact same condition, the only difference is the thickness change according to the displacement.