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Reference: ParaView Version 4.3.1 I have two technical questions: (Q1) In the PV filter 'Gradient Of Unstructured Data Set' is the "QCriterion" function, the Q-Criterion defined by J. C. R. Hunt, A. Wray, and P. Moin (1988) "Eddies, stream, and convergence zones in turbulent flows," Center for Turbulence Research Report CTR-S88, and referenced by G. Haller in "An objective definition of a vortex," J. Fluid Mech. (2005), vol. 525, pp.1–26? (Answer to Q1) Courtesy of Don Simons of Egility Corp., Yes, the formula being Q=-0.5*(Vx,x*Vx,x + Vy,y*Vy,y + Vz,z*Vz,z) - (Vx,y*Vy,x + Vx,z*Vz,x + Vy,z*Vz,y) (Q2) In the PV filter 'Calculator' what is the formula used by the "mag" function to calculate mag(S) where S is a symmetric 2nd-order tensor? Using matrix notation, the tensor S would have the following components: --------------- | Sxx Sxy Sxz | | Sxy Syy Syz | | Sxz Syz Szz | --------------- (Answer to Q2) The PV formula for mag(S) is the square root of the sum of the squares of the 6-tuple (Sxx, Syy, Szz, Sxy, Sxz, Syz). For consistency with a three-component vector, I would have expected it to be the 6-tuple (Sxx, Syy, Szz, 2Sxy, 2Sxz, 2Syz)? Samuel W Key FMA Development, LLC 1005 39th Ave NE Great Falls, Montana 59404 USA |
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