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2-D Model in CFX

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Old   August 2, 2005, 07:22
Default 2-D Model in CFX
  #1
Akin
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Hello, I am curious how to run a 2-d model in CFX5, I understand you have to set an enviroment variable to do it (how ?) and also have your mesh extruded how ? I am still using CFX-build, can any one kindly give a step by step method or point me to some literature and example please. Thanks
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Old   August 3, 2005, 11:24
Default Re: 2-D Model in CFX
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Sebastian Spring
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Hi there,

as far as I know CFX-5 cannot simulate 2D problems. It will always require a 3D mesh. But you can then use only 1 cell in the direction normal to the symmetry plane, so it is almost 2D.
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Old   August 3, 2005, 18:31
Default Re: 2-D Model in CFX
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Glenn Horrocks
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Hi,

You are correct, CFX5 cannot do 2D simulations but you can turn a 2D planar or axisymmetric mesh into a 3D mesh by extruding or rotating one element thick and placing symmetry planes on the front and back faces. The solver then uses the 3D solver on this mesh and the symmetry planes prevent flows in the third dimension.

I know the developers have been asked to include a 2D solver in CFX5, I guess it is probably one of the most requested features for CFX. But as there is a work around available and it requires the entire solver to be rejigged it has not been done - alas, a real 2D solver would be very nice and much more efficient.

As for your request as to how to generate a 2D mesh in CFX-Build, have a look at the CFX-Community. There are a number of reports on how to do it there.

Regards, Glenn Horrocks
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Old   August 8, 2005, 15:38
Default Re: 2-D Model in CFX
  #4
Paul Lewis
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Hi Glenn,

You mention rotating the 2D model to one element thick, this would make a wedge for axisymmetric problems. How do you deal with the mesh near the axis of rotation (the point of the wedge), surely the mesh cells start to become very distorted with high aspect ratios? This would then probably lead to convergence problems.

Regards

Paul

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Old   August 8, 2005, 18:51
Default Re: 2-D Model in CFX
  #5
Glenn Horrocks
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Hi Paul,

Yes, it does lead to elements with high aspect ratios which can cause convergence problems. This is partly mitigated by the fact that the flow is aligned with the element faces so the high aspect ratio elements are not as bad as when they are in a 3D flow.

Regards, Glenn Horrocks
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