# Is it possible to nest a rotating domain inside of another rotating domains?

 It`s certainly possible to have rotating domain that is completely surrounded by another rotating domain, but the rotational motion of the inner domain is not superimposed on the rotational motion of the outer domain. In the general case the inner rotation can be accounted for using the moving mesh feature while the outer rotation is accounted for using a rotating domain, in which case only a single domain in needed. The disadvantage of using a moving mesh to simulate rotating components is that the simulation is always transient and you generally need a small timestep compared to a rotating domain approach.Another approach is to account for the inner rotation by setting a wall velocity about a local coordinate axis. However, this is only valid when the wall velocity is tangential to the local rotation axis, e.g. a cylinder rotating about its local axis; this would not work for a blade. The CFX Solver accepts the following CCL to set this type of boundary condition (CFX-Pre does not accept this CCL):FLOW: DOMAIN: Rotating Domain BOUNDARY: Local Rotating Wall Boundary Type = WALL Frame Type = Rotating Location = MyWall1 BOUNDARY CONDITIONS: WALL INFLUENCE ON FLOW: Option = No Slip WALL VELOCITY: Angular Velocity = 200 [radian s^-1] Option = Rotating Wall AXIS DEFINITION: Option = Coordinate Axis Rotation Axis = Coord 1.3 END END END WALL ROUGHNESS: Option = Smooth Wall END END END ENDENDThis CCL will rotate the wall about the z-axis of the local coordinate frame "Coord 1". The entire wall is also within a rotating domain rotating about a different axis.