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2D Simulation in CFX

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Old   August 3, 2010, 05:04
Default 2D Simulation in CFX
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Pavelistyj
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Hi ,

Is there an option of 2D simulations in CFX ?
Please help to begin ...

Thanks,
Pavelko .
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Old   August 3, 2010, 05:15
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CCTech
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Yes, you can simulate 2D cases. For example, if you import a Fluent 2D mesh in CFX, CFX will extrude the 2D mesh in third direction by 1 element thick.

Refer to CFX help at this location


Modeling 2D Problems


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Old   August 3, 2010, 08:03
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Glenn Horrocks
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http://www.cfd-online.com/Wiki/Ansys..._simulation.3F
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Old   August 5, 2010, 16:25
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I'm just kind of thinking aloud here. If the mesh is only 1 element thick and a tet mesh is used, wouldn't there be a gradient in that direction? I suppose that it should be independent of the choice of element. I'm just trying to understand what is going on behind the scenes.

This would not work if there was an obstacle in the flow, correct? That is, this would not work for an external flow? I suppose it should work as long as the solid and liquid have the same length.

Thanks for any thoughts as the CFX documentation is extremely limited. The only CFX document which appears to have anything on the subject is the Solver Modeling Guide which says

• Make the mesh only 1 element thick. More elements will slow computational time and require more memory.
• For planar 2D geometries, apply symmetry conditions to the front and back planes. Free Surface Flow Over a Bump is one example of a case that uses this setup. Do not use free slip walls; doing so will hurt accuracy because control volume gradients will not be computed. The extrusion distance should be on the order of the smallest mesh dimension.
• For axisymmetric 2D geometries, apply symmetry conditions to the high-theta and low-theta planes unless there is swirl anticipated in the flow, in which case, 1:1 periodic connections should be applied instead. Do not use GGI periodic connections; doing so will hurt accuracy. The extrusion rotation angle for axisymmetric geometries should be small (for example, 1 to 5 degrees).
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Old   August 5, 2010, 19:04
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You can use tet elements but the problem there is that there has to be variable gradients in the element which keep the Z direction gradients 0. This is harder to maintain than hex elements aligned with the Z axis and in that case the Z axis gradient is trivial.
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