<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: times new roman,new york,times,serif; font-size: 12pt; color: #000000'>David,<br><br>I haven't taken on lambda-2 yet, but I have been able to build a pipeline for Q-Criterion. It looks something like:<br><br>Data -> CellDataToPointData (if it isn't already point data) -> ComputeDerivatives (set the gradient option to vorticity and the tensor option to strain) -> CellDataToPointData -> Calculator (compute |S|^2) -> Calculator (compute |\Omega|^2) -> Calculator (compute Q-criterion)<br><br>Since lambda_2 = S_ik S_ij + \Omega_ik \Omega_kj, you can use the same procedure and use just the standard calculators if you want to expand the Einstein summation and plug them all. <br><br>Once I've done this, I save the set of 3 calculators as a custom filter. When I use pvpython, I load my custom filter in the server manager and then use the CD2PD and ComputeDerivatives filters as needed. The python calculator might be a better way to do it, but I haven't tried that yet.<br><br>Tim<br><br><hr id="zwchr"><div style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From: </b>"David Larsson" <david.larsson@sth.kth.se><br><b>To: </b>paraview@paraview.org<br><b>Sent: </b>Monday, December 7, 2015 4:11:39 PM<br><b>Subject: </b>[Paraview] Velocity field analysis - lambda2<br><br>
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<p><font size="2">Dear all, </font></p>
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<p><font size="2">I'm working with velocity vector fields over multiple time steps. I would like to compute a number of entities for the velocity field - most importantly the lambda2-scalar, but being relatively new to paraview I'm not really sure how to do
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<p><font size="2">I can do some simple modifications using the calculator but can't really find my way to grad() or curl() etc. I guess the solution is going over to pvpython (which would also be preferred with regards to doing automated analysis).</font></p>
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<p><font size="2">Does anyone have any experience with performing numerical analysis of vector velocity fields in pvpython that could give some hints on how to get started? Or does anyone even have performed lambda2-analysis on such?
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<p><font size="2">I've seen some similar questions in the mail-list from before but can't seem to find a conclusive answer, so I thought I'd give it a try myself.</font></p>
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<p><font size="2">Thanks for the help.</font></p>
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<p><font size="2">/David<br>
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