TY - JOUR A1 - Kasten, Jens A1 - Petz, Christoph A1 - Hotz, Ingrid A1 - Hege, Hans-Christian A1 - Noack, Bernd A1 - Tadmor, Gilead T1 - Lagrangian Feature Extraction of the Cylinder Wake JF - Physics of Fluids Y1 - 2010 U6 - https://doi.org/10.1063/1.3483220 VL - 22 IS - 9 SP - 091108 ER - TY - CHAP A1 - Kasten, Jens A1 - Weinkauf, Tino A1 - Petz, Christoph A1 - Hotz, Ingrid A1 - Noack, Bernd R. A1 - Hege, Hans-Christian T1 - Extraction of Coherent Structures from Natural and Actuated Flows T2 - Active Flow Control II Y1 - 2010 SN - 978-3-642-11734-3 U6 - https://doi.org/10.1007/978-3-642-11735-0_24 VL - 108 SP - 373 EP - 387 PB - Springer, Berlin ER - TY - CHAP A1 - Kasten, Jens A1 - Petz, Christoph A1 - Hotz, Ingrid A1 - Noack, Bernd R. A1 - Hege, Hans-Christian ED - Magnor, Marcus ED - Rosenhahn, Bodo ED - Theisel, Holger T1 - Localized Finite-time Lyapunov Exponent for Unsteady Flow Analysis T2 - Vision Modeling and Visualization Y1 - 2009 SN - 978-3-9804874-8-1 VL - 1 SP - 265 EP - 274 PB - Universität Magdeburg, Inst. f. Simulation u. Graph. ER - TY - JOUR A1 - Kasten, Jens A1 - Reininghaus, Jan A1 - Hotz, Ingrid A1 - Hege, Hans-Christian A1 - Noack, Bernd A1 - Daviller, Guillaume A1 - Morzyński, Marek T1 - Acceleration feature points of unsteady shear flows JF - Archives of Mechanics N2 - A framework is proposed for extracting features in 2D transient flows, based on the acceleration field to ensure Galilean invariance. The minima of the acceleration magnitude, i.e. a superset of the acceleration zeros, are extracted and discriminated into vortices and saddle points --- based on the spectral properties of the velocity Jacobian. The extraction of topological features is performed with purely combinatorial algorithms from discrete computational topology. The feature points are prioritized with persistence, as a physically meaningful importance measure. These features are tracked in time with a robust algorithm for tracking features. Thus a space-time hierarchy of the minima is built and vortex merging events are detected. The acceleration feature extraction strategy is applied to three two-dimensional shear flows: (1) an incompressible periodic cylinder wake, (2) an incompressible planar mixing layer and (3) a weakly compressible planar jet. The vortex-like acceleration feature points are shown to be well aligned with acceleration zeros, maxima of the vorticity magnitude, minima of pressure field and minima of λ2. Y1 - 2016 VL - 68 IS - 1 SP - 55 EP - 80 ER -