Why Ansys Merge zones automatically after meshing
 

My model is Wind turbine
it consist of two parts, first around the blade (MRF) and second is the huge enclosure (stationary)
After meshing in fluent , ansys consider the two domains is one interior zone (by merge them automatically)

how can i fix this problem
I used automatic meshing option

You mean there isn't internal wall between fluid and blade zones ?

you model by Workbench DesignModeler or SolidWork ? Can you attach modeling file ?

.solidworks
.Two zones are fluid but different in rotation condition. The problem is after meshing,ansys consider their one zone

Are they part of a multi-body part? If so, ANSYS will mesh them conformally, but your solver can still see them as separate fluid zones so you can apply your rotating boundary condition.

I should add that if you don't want them to have conformal mesh, just make sure the bodies are in separate parts. This is all managed in the part tree.