Please download the word document, which contains the details on setting up the Python Calculator filter to calc lambda2, and use the advanced option of ‘Gradient’ filter to calculate vorticity, Q-Criterion.
This code is not tested, some user has already report error, please use it as a starting point in your application.
eigenvalue(strain(Velocity)**2 + (Gradients – strain(Velocity)**)2)
it should be
eigenvalue(strain(Velocity)**2 + (Gradients – strain(Velocity))**2)
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Author: Qingfeng XIA
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please keep the original link in your reference.