Hi Andy,
ok - try to do the job with a programmable filter:
importnumpyasnp
fromnumpyimportlinalg asLA
fromparaview.numpy_supportimportvtk_to_numpy
input0 =inputs[0]
# Test NumPy
w, v =LA.eig(np.diag((1, 2, 3)))
printw
printv
npArr =vtk_to_numpy(input0.PointData["val"])
The test with the eig-function works fine. However - i have to convert
the val-Tensor from VTK to NumPy to work with NumPy. I use therefore the
vtk_to_numpy function - but it gives
Traceback (most recent call last):
File "<string>", line 22, in <module>
File "<string>", line 19, in RequestData
File
"/opt/PARAVIEW_5_4_0_OpenGL2/ParaView-v5.4.0.bin/lib/site-packages/paraview/numpy_support.py",
line 213, in vtk_to_numpy
typ = vtk_array.GetDataType()
AttributeError: 'VTKCompositeDataArray' object has no attribute
'GetDataType'
[ 1. 2. 3.]
[[ 1. 0. 0.]
[ 0. 1. 0.]
[ 0. 0. 1.]]
What did i wrong?
Stefan
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
<mailto: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
<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 <mailto: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
<https://en.wikipedia.org/wiki/Lambda2_method>) with
ParaView. The way of calculation is based on this link
http://www.iesensor.com/blog/2016/01/24/using-paraview-to-visualise-vorticity-lambda2-vorticity-q-criterion/
<http://www.iesensor.com/blog/2016/01/24/using-paraview-to-visualise-vorticity-lambda2-vorticity-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
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o High-Lift Aerodynamics Email : stefan.mel...@dlr.de
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