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Is the flow 2D or 3D if I used periodic interface?

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Old   February 13, 2020, 19:03
Default Is the flow 2D or 3D if I used periodic interface?
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Andro
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Hello,

If I used periodic interface in CFX, is the flow 2D or 3D? I know that if I used small thickness and symmetric boundary for the front and back face of the domain, the flow considered 2D. Please, can anyone help me to understand this point?

Thanks In advance,
A.M.
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Old   February 13, 2020, 19:36
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Glenn Horrocks
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Are you are asking what is the difference between a 2D model with symmetry planes on top and bottom Z faces (assuming the flow is in the XY plane), and replacing those symmetry planes with translational periodic boundaries?

If that is your question: The symmetry plane approach is closest to a true 2D simulation as no flow in the third dimension is possible. The periodic boundary approach allows flow in the third dimension, but that flow is the same at all Z values. The periodic approach is useful in axisymmetric flows with swirl as the third dimension can capture the swirl effect.
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Old   February 13, 2020, 19:48
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Yes, this is my question. If I want to make a heave mode for airfoil, which is 2D shape. What should I considered, periodic boundary or symmetry? Thanks.
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Old   February 14, 2020, 07:01
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Have a think about what my previous post said. You should be able to work it out from that. You need to understand these options for you to be able apply them.
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