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Combining CG Motion and Grid Motion Macros in Fluent

    • Christopher Pass

      Hi there,

      I am trying to model a case in which one cell zone in my domain will undergo both rigid body motion and deforming motion. I have defined the rigid body motion in a UDF using the DEFINE_CG_MOTION macro, this motion is working fine. 

      I have specified the deforming motion using the DEFINE_GRID_MOTION macro, I had a version of this UDF in which I was defining node positions on the deforming boundary explicitly, this did not work so I have modified this by using the NODE_COORD_NEST macro which I believe should specify the deforming motion relative to the CG motion of the whole zone.

      My workflow is to:

      1. Compile DEFINE_CG_MOTION and DEFINE_GRID_MOTION macros.
      2. Setup rigid body deformation on relevant cell zones.
      3. Setup 'user-specified' mesh deformation on deforming boundary.
      4. Set the user-specified mesh deformation to occur relative the CG motion of the adjacent cell zone.

      This seems to be working in that I can clearly see CG motion as specified and I can also see motion of the boundary nodes. The issue is that, despite setting a deforming thread flag (SET_DEFORMING_THREAD_FLAG) to define the adjacent cell zone as deforming, I dont see any deformation of the interior mesh so I get inverted elements immediately. 

      Can anyone offer any advice? I have searched this forum and also dug through the documentation to no avail so any guidance would be appreciated!


    • C N
      Ansys Employee

      Hello christopher,

      You have raised a SR and I am working on it. As discussed , It is most probably the udf not working properly . Kindly check on it. I will update you regarding this on the service requestal portal


      Chaitanya Natraj

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