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Vortex and Strain Skeletons in Eulerian and Lagrangian Frames Corresponding Publication
Logo We present an approach to analyze mixing in flow fields by extracting vortex and strain features as extremal structures of derived scalar quantities that satisfy a duality property: they indicate vortical as well as high-strain (saddle-type) regions. Specifically, we consider the Okubo-Weiss criterion and the recently introduced Mz-criterion. While the first is derived from a purely Eulerian framework, the latter is based on Lagrangian considerations. In both cases high values indicate vortex activity whereas low values indicate regions of high strain. By considering the extremal features of those quantities, we define the notions of a vortex and a strain skeleton in a hierarchical manner: the collection of maximal 0D, 1D and 2D structures assemble the vortex skeleton; the minimal structures identify the strain skeleton. We extract those features using scalar field topology and apply our method to a number of steady and unsteady 3D flow fields. J. Sahner, T. Weinkauf, N. Teuber, H.-C. Hege
Vortex and Strain Skeletons in Eulerian and Lagrangian Frames
IEEE Transactions on Visualization and Computer Graphics 13(5), September - October 2007
[slideshow]
In the flow around an airfoil, scaled lines of maximal strain (blue) and lines of maximal vortex activity (red) give a complete overview of location, extent and strength of these important flow features.
In the flow around an airfoil, scaled lines of maximal strain (blue) and lines of maximal vortex activity (red) give a complete overview of location, extent and strength of these important flow features.
Core lines of maximal vortex activity in a turbulent mixing layer. The lines have been scaled according to the Q-criterion.
Core lines of maximal vortex activity in a turbulent mixing layer. The lines have been scaled according to the Q-criterion.
ABCUnsteadyVolrenPathLines
ABCUnsteadyVolrenPathLines
AttractingNodeISL
AttractingNodeISL
AttractingNodeSaddleISL
AttractingNodeSaddleISL
CylinderMzExplain
CylinderMzExplain
CylinderQExplain
CylinderQExplain
CylinderQExplain_VortexLines
CylinderQExplain_VortexLines
CylinderQIsoSplitUp
CylinderQIsoSplitUp
CylinderQSkeletonFull
CylinderQSkeletonFull
DifferenceDiscreteContinuousSaddle2
DifferenceDiscreteContinuousSaddle2
DiscreteMinimaIso
DiscreteMinimaIso
DiscreteSaddleIso
DiscreteSaddleIso
MixingLayerFrameOfReferenceOriginal
MixingLayerFrameOfReferenceOriginal
MixingLayerMzMixingLines
MixingLayerMzMixingLines
MixingLayerQIsoTeaser
MixingLayerQIsoTeaser
MixingSkeletonFull
MixingSkeletonFull
MixingSkeletonLines
MixingSkeletonLines
RepellingNodeISL
RepellingNodeISL
RepellingNodeSaddleISL
RepellingNodeSaddleISL
RepellingSaddleSep
RepellingSaddleSep
SCCH25dExplain
SCCH25dExplain
SCCH25DVortexAndMixingIso
SCCH25DVortexAndMixingIso
VortexLineSeparated
VortexLineSeparated
VortexSkeletonFull
VortexSkeletonFull
VortexSkeletonLines
VortexSkeletonLines
WatershedHeightRideCompareFront
WatershedHeightRideCompareFront
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