How does Paraview compute spatial derivatives at boundaries

Development
1

Hi,

I am using the “Gradient of Unstructured Data Set” filter to calculate the curl and divergence of a 3D field. How does Paraview compute the derivatives on domain boundaries?

In my case, one boundary of the domain (say, x = 0) is a symmetry boundary. But I don’t think Paraview knows this since it is not specified in the solution file (in exo format).

After running “Gradient of Unstructured Data Set”, I observe a significant difference in divergence between the x = 0 plane and any other plane that is slightly into the domain (say, x = 0.0001). I am not sure how to interpret this…

Any help is highly appreciated!

Thanks,
Kevin

2

It doesn’t.

Here the documentation of the underlying Graddient filter:
https://vtk.org/doc/nightly/html/classvtkGradientFilter.html

And the source code :
https://gitlab.kitware.com/vtk/vtk/blob/master/Filters/General/vtkGradientFilter.cxx

3

Thanks, Matt!