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CFD versus Structural Meshing

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Old   April 21, 2010, 16:40
Default CFD versus Structural Meshing
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Why does it take only a few minutes to mesh for a structural mesh and from several minutes up to hours to mesh for CFD? It seems that ANSYS uses the same meshing program regardless of the type of analysis?

Thank you for any help!
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Old   June 8, 2010, 20:04
Default Physics based defaults.
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Is this because the CFD mesh has a lot more elements?

In ANSYS Meshing, you tell it the physics (CFD, EMAG, FEA, Explicit) and it sets up your defaults to give a reasonable mesh. For instance, if you said FEA, it would know that you need a coarse mesh, probably quadratic Tets or Swept Hexa. If you chose EMAG, the tetras would have mid nodes, but would still be linear. If you chose CFD and you had "Program controlled inflation" on, it would know to give you a much finer mesh with linear tets or hexas, a sizing function to keep several cells across any gap and inflation (prisms or hexas) along walls (but not along Inlet, outlet or symmetry planes). In fact, it is smart enough to mesh differently if you tell it CFD-Fluent vs CFD-CFX, based on the specific needs of each solver.

On a given model, the FEA default mesh could be only a few thousand elements, where as the mesher would insert millions of cells to resolve the same volume for CFD. Those extra elements with higher quality requirements take more time.

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