POLYFLOW - Severe inaccuracies of the velocity field for flow cases involving periodic boundary conditions


Some simulation cases involving periodic boundary conditions, exhibit somewhat severe inaccuracies in the velocity field. A careful inspection of the geometry has revealed that the trouble may originate from the discretisation on both boundaries in periodic relationship. More precisely, after applying the geometric transformation for periodic boundary conditions, the mesh nodes at these boundaries did not exactly coincide. In some cases, this may have desastrous consequences.

This can be fixed by invoking POLYDATA with the keyword PERIODIC_FOR_COORD in the .p3rc file. Still, the user is expected to generate the grid in such a way that the boundaries in periodicity relationship nearly coincide with eachother. The use of the keyword will make sure that the coordinates coincide numerically upon transformation. The discretisation will not be altered.





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