[Paraview] Fwd: Question about strain from filter: Compute Derivatives -> Vector -> Strain.... type?

[Andy Bauer]

Hi Tim,

The class that does that computation is called vtkCellDerivatives. It looks
like the part of that code that does the strain computation is:
          tens->SetComponent(0,0, derivs[0]);
          tens->SetComponent(0,1, 0.5*(derivs[1]+derivs[3]));
          tens->SetComponent(0,2, 0.5*(derivs[2]+derivs[6]));
          tens->SetComponent(1,0, 0.5*(derivs[1]+derivs[3]));
          tens->SetComponent(1,1, derivs[4]);
          tens->SetComponent(1,2, 0.5*(derivs[5]+derivs[7]));
          tens->SetComponent(2,0, 0.5*(derivs[2]+derivs[6]));
          tens->SetComponent(2,1, 0.5*(derivs[5]+derivs[7]));
          tens->SetComponent(2,2, derivs[8]);

My suggestion would be to use one of the gradient filters (either Compute
Derivatives or Gradient of Unstructured Data Sets) and then either use the
Calculator filter (slower but simpler) or the Python Programmable filter
(faster but more complicated) to compute your desired results.

Regards,
Andy


On Thu, Mar 13, 2014 at 3:23 PM, Tim Bhatnagar <tim.bhatnagar at gmail.com>wrote:

> Fair enough.... I'd like to think that since the infinitesimal strain
> tensor is just a simplified version of the Green-Lagrange tensor (really,
> some usually-small terms just get assumed to be zero), that the Paraview
> designers utilized a fully-designed Green-Lagrange formulation, which will
> approximate to the infinitesimal strain tensor then the strains are small...
>
> But it'd be great to get a definitive answer.. otherwise I ened to think
> about creating my own filter to determine the finite strain tensor.
>
> Thanks for the comment,
>
> Tim
>
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