mixing_elbow.vtk is an invalid VTK dataset

[ahernsean]

🔍 Before submitting the issue

• I have searched among the existing issues
• I am using a Python virtual environment

🐞 Description of the bug

The mixing_elbow.vtk dataset does render in most VTK pipelines. However, VTK's cell validator (vtkCellValidator) shows fundamental problems with the grid. Almost every cell has a validity value of 52 (110100 in binary), indicating that they are invalidate due to IntersectingEdges, NoncontiguousEdges, and Nonconvex.

📝 Steps to reproduce

Two ways to reproduce:

1. Add a vtkCellValidator to a VTK pipeline. Look at the resulting values of the ValidityState scalar. They should be all zero. If they are not, look at the reference in vtkCellValidator.h.
2. Load the dataset in ParaView. Add a ValidateCells filter. Change the coloring to the ValidityState scalar. The meaning is the same as in number 1 above.

💻 Which operating system are you using?

Windows

📀 Which ANSYS version are you using?

Doesn't matter

🐍 Which Python version are you using?

3.9

📦 Installed packages

I validated using ParaView

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[ahernsean]

Update: We've been working with Kitware to resolve problems with various element shapes within VTK unstructured grids. They've provided some fixes in VTK 9.5, but a more comprehensive fix (dynamic adaptive thresholds for validity tests) won't come until VTK 9.6, which is expected near the end of the year. See more info at https://github.com/orgs/ansys-services/projects/71?pane=issue&itemId=119834047&issue=ansys-services%7Ckitware-ansys%7C4