POLYFLOW - symmetry condition seems lost for a free surface flow.

Symmetry conditions is defined on a boundary for a free surface flow, and does not seem to be verified in the calculation. It is observed e.g. that the free jet twists about the direction of extrusion.

This may happen when the symmetry condition is applied on a boundary that does not have a unique normal direction. A rather typical scenario is when that boundary consists of two perpendicular planes: at the intersection line (edge), the "normal" direction is evaluated on the basis of the local element size. Therefore actual perpendicularity can no longer be guaranteed. The remedy would consist of defining symmetry condition on boundaries that have a unique perpendicular direction. For the scenario suggesed above, the boundary should be split.

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