[vtkusers] How does vtk compute gradients on unstructured mesh?

[Emilie Sauvage]

Dear vtk users & developers,

 could you please explain how does vtk compute gradients on a tetrahedral
mesh with node - based data? I have a data file as a result of a finite
element cfd simulation and need to compute velocity gradients in order to
obtain wall shear stress. I would like to have a bit of information about
what happens in vtk/paraview in order to understand how accurate is the
obtained wall shear stress field.

Does vtk for example use the P1 shape functions to compute gradients in
cells? Some averaging of these gradients could give gradients in nodes.

Thank you very much.

Best regards.

Emilie Sauvage