moving mesh interface meets with water-air free surface
 

I am doing a two phase flow simulation(water-air free surface) with a cross stirring between them.the water-air interface goes through the center of cross.At initialization ,the water is at rest .When the calculation runs,the water inside the moving zone rotates with the angular velocity that is the same as the moving zone .I wonder if the water can be still from beginning to end.Is there anyone knowing how to reallize it in Fluent.

can you post an illustrated schematic for your problem it will be more understandable if you post it?