[bramdiff]

Dear All,

I am writing as I am having trouble with rotating objects in CFX. In the attached image, case 1 refers to what I am trying to model. This is a flap rotating about its centroid, at a fixed user specified angular velocity, as well as also rotating about the global Z axis, at another user specified angular velocity. If I understand correctly I am unable to use the rotating domain option twice, as the region around the flap is rotating about an axis that is moving, so I have started to try and learn moving mesh.

I set up a simpler model- case 2, to try and get moving mesh to work. Using two domains and cylindrical components to specify mesh displacement the model ran fine. However this was still displacement relative to a fixed rotational axis. So what I have been trying to do (and here is where the errors start flying in) is specify the same mesh rotation using Cartesian components, so it can all be relative to the global coordinate system.

Would anyone be able to help me with the equations for the x,y,z components of displacement, or am I being naive and is it a lot harder than that? I am also unsure as to whether i should (for case 2 in the attached image) have two domains with an interface like a normal rotating domain problem, or one domain with a sub-domain?

The error message is that negative elements are being created, so I’m guessing my expressions aren’t correct and that the mesh is deforming, as mentioned when I ran it with cylindrical components the mesh rotated fine.
Any ideas/ help is greatly appreciated, and if you need more information about the problem just let me know!

Thanks,

James


MovingMesh.jpg