<div dir="ltr">Hi,<div><br></div><div>The best way to do this would be in a programmable filter. I'm guessing numpy has some method to compute eigenvalues for non-symmetric matrices. Beyond that adding the capability to the Python calculator or some other filter would be needed.</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 13, 2017 at 3:35 AM, Stefan Melber <span dir="ltr"><<a href="mailto:Stefan.Melber@dlr.de" target="_blank">Stefan.Melber@dlr.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div class="m_5477797258878518425moz-cite-prefix">Hi Andy,<br>
<br>
i think i found the reason: i need the computation of
(unsymmetrical) eigenvalues for lambda2 - however it seems that
the function "eingenvalue" calculates only symmetric ones (see
<a class="m_5477797258878518425moz-txt-link-freetext" href="https://www.paraview.org/ParaView/Doc/Nightly/www/py-doc/paraview.vtk.numpy_interface.algorithms.html" target="_blank">https://www.paraview.org/<wbr>ParaView/Doc/Nightly/www/py-<wbr>doc/paraview.vtk.numpy_<wbr>interface.algorithms.html</a>).
How can i calculate the unsymmetric ones with ParaView?<br>
<br>
Best regards,<br>
<br>
Stefan<br>
<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr">Hi,
<div><br>
</div>
<div>Maybe compute each portion manually and check that against
the correct values. Also, verifying the gradient calculation
is correct is another thing to look at. If the grid isn't
specified properly then the gradient operation will likely be
wrong.</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Fri, Jun 9, 2017 at 8:46 AM, Stefan
Melber <span dir="ltr"><<a href="mailto:Stefan.Melber@dlr.de" target="_blank">Stefan.Melber@dlr.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote">
<div> Hi,<br>
<br>
<br>
for vortex-detection i (tried) to calculate the
lambda2-criterion (see e.g. <a class="m_5477797258878518425m_6725794015711734747moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Lambda2_method" target="_blank">https://en.wikipedia.org/wiki/<wbr>Lambda2_method</a>)
with ParaView. The way of calculation is based on this
link <a class="m_5477797258878518425m_6725794015711734747moz-txt-link-freetext" href="http://www.iesensor.com/blog/2016/01/24/using-paraview-to-visualise-vorticity-lambda2-vorticity-q-criterion/" target="_blank">http://www.iesensor.com/blog/2<wbr>016/01/24/using-paraview-to-vi<wbr>sualise-vorticity-lambda2-vort<wbr>icity-q-criterion/</a>.<br>
<br>
However - the results are a kind of "wrong" - see attached
pictures: l2_solver.png shows what the flow solver writes
out for lambda2, l2_paraview.png shows what calculated
with the algorithm below.<br>
<br>
Calculation of lambda2:<br>
<br>
<tt>D = Gradients = [d_ij]</tt><tt><br>
</tt><tt>S = strain(Vel)</tt><tt><br>
</tt><tt><br>
</tt><tt>S = (D + D^T)/2</tt><tt><br>
</tt><tt>Omega = (D - D^T)/2</tt><tt><br>
</tt><tt><br>
</tt><tt>lambda = EigenValue_of(S^2 + Omega^2) </tt><tt><br>
</tt><tt> = EigenValue_of(S^2 + (D - S)^2) </tt><tt><br>
</tt><tt> = EigenValue_of(S^2 + (Gradients -
strain(vel))^2) </tt><tt><br>
</tt><tt> </tt><tt><br>
</tt><tt>lambda2 = lambda_Y</tt><tt><br>
</tt><br>
and in ParaView this mean<br>
<br>
<tt>o Vector of velocity with
"Calculator".................: Vel =
iHat*x_velocity+jHat*y_velocit<wbr>y+kHat*z_velocity</tt><tt><br>
</tt><tt>o Gradients of Vel with "GradientOfUnstructuredDataSet<wbr>":
switch on "compute gradient" and name it "Gradients"</tt><tt><br>
</tt><tt>o Calculate lambda with
"PythonCalculator"............<wbr>.: lambda =
eigenvalue(strain(Vel)**2+(Gra<wbr>dients -
strain(Vel))**2)</tt><tt><br>
</tt><tt>o Caluclate lambda2 with
Calculator....................<wbr>: lambda2 = lambda_Y</tt><tt><br>
</tt><br>
<br>
<br>
Does anyone see the error why the calculation of lambda2
with ParaView does not work?<br>
<br>
Remark: i contacted the author of the blog above already -
seems he never tested his calculation and has no idea what
is "wrong".<br>
<br>
Stefan<br>
<br>
<br>
<br>
<tt>==============================<wbr>==============================<wbr>====</tt><tt><br>
</tt><tt> <wbr>
</tt><tt><br>
</tt><tt> _/ <b>Dr.
Stefan Melber-Wilkending</b></tt><tt><br>
</tt><tt> _/_/
</tt><tt><br>
</tt><tt> _/ _/ Deutsches
Zentrum für Luft- </tt><tt><br>
</tt><tt> _/_/_/_/_/_/_/_/_/_/ und
Raumfahrt e.V. (DLR) </tt><tt><br>
</tt><tt> _/ _/ _/
_/ <wbr> </tt><tt><br>
</tt><tt> _/ _/ _/ _/ German
Aerospace Center </tt><tt><br>
</tt><tt> _/_/_/_/_/_/_/_/_/_/ <wbr>
Institute of Aerodynamics </tt><tt><br>
</tt><tt> _/ _/ _ _ and Flow
Technology </tt><tt><br>
</tt><tt> _/_/ | \ | |_| Transport
Aircraft Branch </tt><tt><br>
</tt><tt> _/ |_/ |_ |
\ <wbr> </tt><tt><br>
</tt><tt> <wbr>
Lilienthalplatz 7 </tt><tt><br>
</tt><tt> Fields of activities: 38108
Braunschweig</tt><tt> <br>
</tt><tt> <wbr>
Germany</tt><tt> <br>
</tt><tt> o Numerical Windtunnel
Simulation <wbr> </tt><tt><br>
</tt><tt> o Aero-Acoustic Windtunnel Design Phone : +49
<a href="tel:%28531%29%20295-2836" value="+15312952836" target="_blank">531/295-2836</a>
</tt><tt><br>
</tt><tt> o Numerical Optimization Fax. .: +49
<a href="tel:%28531%29%20295-2914" value="+15312952914" target="_blank">531/295-2914</a>
</tt><tt><br>
</tt><tt> o Visualization Techniques <wbr>
</tt><tt><br>
</tt><tt> o High-Lift Aerodynamics Email : <a class="m_5477797258878518425m_6725794015711734747moz-txt-link-abbreviated" href="mailto:Stefan.Melber@DLR.de" target="_blank">Stefan.Melber@DLR.de</a></tt><tt><br>
</tt><tt> o Glider-Aerodynamics <wbr> Web ..:
<a class="m_5477797258878518425m_6725794015711734747moz-txt-link-freetext" href="http://www.dlr.de/AS" target="_blank">http://www.dlr.de/AS</a></tt><tt><br>
</tt> <wbr> <wbr> <wbr>
<br>
<tt>==============================<wbr>==============================<wbr>====</tt><tt><br>
</tt><br>
</div>
<br>
______________________________<wbr>_________________<br>
Powered by <a href="http://www.kitware.com" rel="noreferrer" target="_blank">www.kitware.com</a><br>
<br>
Visit other Kitware open-source projects at <a href="http://www.kitware.com/opensource/opensource.html" rel="noreferrer" target="_blank">http://www.kitware.com/opensou<wbr>rce/opensource.html</a><br>
<br>
Please keep messages on-topic and check the ParaView Wiki
at: <a href="http://paraview.org/Wiki/ParaView" rel="noreferrer" target="_blank">http://paraview.org/Wiki/ParaV<wbr>iew</a><br>
<br>
Search the list archives at: <a href="http://markmail.org/search/?q=ParaView" rel="noreferrer" target="_blank">http://markmail.org/search/?q=<wbr>ParaView</a><br>
<br>
Follow this link to subscribe/unsubscribe:<br>
<a href="http://public.kitware.com/mailman/listinfo/paraview" rel="noreferrer" target="_blank">http://public.kitware.com/mail<wbr>man/listinfo/paraview</a><br>
<br>
</blockquote>
</div>
<br>
</div>
</blockquote>
<p><br>
</p>
</div>
</blockquote></div><br></div>