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<div>The implementation of the compute derivatives filter has been around a while so the author probably hasn't seen your email. I'm not super familiar with the code, but I believe the vorticity is computed from the first order derivative of the vector field.</div>
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<div>It is not actually using a central difference scheme to compute the gradients. Instead, it is treating the field as a piecewise linear field (or piecewise quadratic or piecewise cubic depending on the cell type) based on the volumes of the cells. The derivatives
are then computed in the middle of the piecewise C1 continuous parts of the cells from the known function.</div>
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<div>You can take a look at the source for the algorithm here:</div>
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<div><a href="http://vtk.org/gitweb?p=VTK.git;a=blob;f=Filters/General/vtkCellDerivatives.cxx;h=4debdf45eeb7a11e98062ab2d9efa65e938433b6;hb=ab4dc579c340167b6b3ae6cd82b3fd645642796a">http://vtk.org/gitweb?p=VTK.git;a=blob;f=Filters/General/vtkCellDerivatives.cxx;h=4debdf45eeb7a11e98062ab2d9efa65e938433b6;hb=ab4dc579c340167b6b3ae6cd82b3fd645642796a</a></div>
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<div>Vorticity is computed between lines 169 and 216.</div>
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<div>-Ken</div>
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<span style="font-weight:bold">From: </span>Jean Hertzberg <<a href="mailto:Hertzberg@Colorado.EDU">Hertzberg@Colorado.EDU</a>><br>
<span style="font-weight:bold">Date: </span>Wednesday, February 11, 2015 at 12:01 PM<br>
<span style="font-weight:bold">To: </span>"<a href="mailto:paraview@paraview.org">paraview@paraview.org</a>" <<a href="mailto:paraview@paraview.org">paraview@paraview.org</a>><br>
<span style="font-weight:bold">Subject: </span>[EXTERNAL] [Paraview] Vorticity calc algorithm?<br>
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<p class="MsoNormal">Hi <o:p></o:p></p>
<p class="MsoNormal">I asked this last week, but got zero response. Please help me, or point me towards the right documentation:<o:p></o:p></p>
<p class="MsoNormal">Exactly what algorithm is used to calculate vorticity in the Compute Derivatives filter? Is it a first or a second order central difference scheme for gradients, or does it use the circulation method?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Jean Hertzberg<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Dept. Mechanical Engineering<o:p></o:p></p>
<p class="MsoNormal">University of Colorado, Boulder<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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