TY - GEN A1 - Reininghaus, Jan A1 - Kasten, Jens A1 - Weinkauf, Tino A1 - Hotz, Ingrid T1 - Combinatorial Feature Flow Fields: Tracking Critical Points in Discrete Scalar Fields N2 - We propose a combinatorial algorithm to track critical points of 2D time-dependent scalar fields. Existing tracking algorithms such as Feature Flow Fields apply numerical schemes utilizing derivatives of the data, which makes them prone to noise and involve a large number of computational parameters. In contrast, our method is robust against noise since it does not require derivatives, interpolation, and numerical integration. Furthermore, we propose an importance measure that combines the spatial persistence of a critical point with its temporal evolution. This leads to a time-aware feature hierarchy, which allows us to discriminate important from spurious features. Our method requires only a single, easy-to-tune computational parameter and is naturally formulated in an out-of-core fashion, which enables the analysis of large data sets. We apply our method to a number of data sets and compare it to the stabilized continuous Feature Flow Field tracking algorithm. T3 - ZIB-Report - 11-02 KW - data analysis KW - feature detection KW - time-varying data KW - topology-based techniques Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-12151 ER - TY - JOUR A1 - Kasten, Jens A1 - Reininghaus, Jan A1 - Hotz, Ingrid A1 - Hege, Hans-Christian T1 - Two-Dimensional Time-Dependent Vortex Regions Based on the Acceleration Magnitude JF - IEEE Transactions on Visualization and Computer Graphics Y1 - 2011 VL - 17 IS - 12 SP - 2080 EP - 2087target ER - TY - JOUR A1 - Reininghaus, Jan A1 - Kotava, N. A1 - Günther, David A1 - Kasten, Jens A1 - Hagen, Hans A1 - Hotz, Ingrid T1 - A Scale Space Based Persistence Measure for Critical Points in 2D Scalar Fields JF - Visualization and Computer Graphics, IEEE Transactions on Y1 - 2011 U6 - https://doi.org/10.1109/TVCG.2011.159 VL - 17 IS - 12 SP - 2045 EP - 2052 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 - TY - GEN 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 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. T3 - ZIB-Report - 15-65 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-58397 SN - 1438-0064 ER - TY - GEN A1 - Kasten, Jens A1 - Reininghaus, Jan A1 - Oberleithner, Kilian A1 - Hotz, Ingrid A1 - Noack, Bernd A1 - Hege, Hans-Christian T1 - Flow over a Cavity – Evolution of the Vortex Skeleton Y1 - 2010 PB - Visualization at 28th Annual Gallery of Fluid Motion exhibit, held at the 63th Annual Meeting of the American Physical Society, Division of Fluid Dynamics (Long Beach, CA, USA, November 21-23, 2010). ER - TY - JOUR A1 - Reininghaus, Jan A1 - Kasten, Jens A1 - Weinkauf, Tino A1 - Hotz, Ingrid T1 - Efficient Computation of Combinatorial Feature Flow Fields JF - Transactions on Visualization and Computer Graphics Y1 - 2012 U6 - https://doi.org/10.1109/TVCG.2011.269 VL - 18 IS - 9 SP - 1563 EP - 1573 ER -