Hi, 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.
On Tue, Jun 13, 2017 at 3:35 AM, Stefan Melber <stefan.mel...@dlr.de> wrote: > Hi Andy, > > 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 https://www.paraview.org/ > ParaView/Doc/Nightly/www/py-doc/paraview.vtk.numpy_ > interface.algorithms.html). How can i calculate the unsymmetric ones with > ParaView? > > Best regards, > > Stefan > > > Hi, > > 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. > > On Fri, Jun 9, 2017 at 8:46 AM, Stefan Melber <stefan.mel...@dlr.de> > wrote: > >> Hi, >> >> >> for vortex-detection i (tried) to calculate the lambda2-criterion (see >> e.g. https://en.wikipedia.org/wiki/Lambda2_method) with ParaView. The >> way of calculation is based on this link http://www.iesensor.com/blog/2 >> 016/01/24/using-paraview-to-visualise-vorticity-lambda2-vort >> icity-q-criterion/. >> >> 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. >> >> Calculation of lambda2: >> >> D = Gradients = [d_ij] >> S = strain(Vel) >> >> S = (D + D^T)/2 >> Omega = (D - D^T)/2 >> >> lambda = EigenValue_of(S^2 + Omega^2) >> = EigenValue_of(S^2 + (D - S)^2) >> = EigenValue_of(S^2 + (Gradients - strain(vel))^2) >> >> lambda2 = lambda_Y >> >> and in ParaView this mean >> >> o Vector of velocity with "Calculator".................: Vel = >> iHat*x_velocity+jHat*y_velocity+kHat*z_velocity >> o Gradients of Vel with "GradientOfUnstructuredDataSet": switch on >> "compute gradient" and name it "Gradients" >> o Calculate lambda with "PythonCalculator".............: lambda = >> eigenvalue(strain(Vel)**2+(Gradients - strain(Vel))**2) >> o Caluclate lambda2 with Calculator....................: lambda2 = >> lambda_Y >> >> >> >> Does anyone see the error why the calculation of lambda2 with ParaView >> does not work? >> >> Remark: i contacted the author of the blog above already - seems he never >> tested his calculation and has no idea what is "wrong". >> >> Stefan >> >> >> >> ================================================================ >> >> _/ *Dr. Stefan Melber-Wilkending* >> _/_/ >> _/ _/ Deutsches Zentrum für Luft- >> _/_/_/_/_/_/_/_/_/_/ und Raumfahrt e.V. (DLR) >> _/ _/ _/ _/ >> _/ _/ _/ _/ German Aerospace Center >> _/_/_/_/_/_/_/_/_/_/ Institute of Aerodynamics >> _/ _/ _ _ and Flow Technology >> _/_/ | \ | |_| Transport Aircraft Branch >> _/ |_/ |_ | \ >> Lilienthalplatz 7 >> Fields of activities: 38108 Braunschweig >> Germany >> o Numerical Windtunnel Simulation >> o Aero-Acoustic Windtunnel Design Phone : +49 531/295-2836 >> <%28531%29%20295-2836> >> o Numerical Optimization Fax. .: +49 531/295-2914 >> <%28531%29%20295-2914> >> o Visualization Techniques >> o High-Lift Aerodynamics Email : stefan.mel...@dlr.de >> o Glider-Aerodynamics Web ..: http://www.dlr.de/AS >> >> >> ================================================================ >> >> >> _______________________________________________ >> Powered by www.kitware.com >> >> Visit other Kitware open-source projects at >> http://www.kitware.com/opensource/opensource.html >> >> Please keep messages on-topic and check the ParaView Wiki at: >> http://paraview.org/Wiki/ParaView >> >> Search the list archives at: http://markmail.org/search/?q=ParaView >> >> Follow this link to subscribe/unsubscribe: >> http://public.kitware.com/mailman/listinfo/paraview >> >> > >
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