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Localized Finite-time Lyapunov Exponent for Unsteady Flow Analysis Jens Kasten1, Christoph Petz1, Ingrid Hotz1, Bernd R. Noack2, Hans-Christian Hege1
 

Summary: Localized Finite-time Lyapunov Exponent for Unsteady Flow Analysis
Jens Kasten1, Christoph Petz1, Ingrid Hotz1, Bernd R. Noack2, Hans-Christian Hege1
1 Zuse Institute Berlin ({kasten,petz,hotz,hege}@zib.de)
2 Berlin Institute of Technology MB1 (Bernd.R.Noack@tu-berlin.de)
Abstract
The Finite-time Lyapunov Exponent (FTLE) is a
measure for the rate of separation of particles in
time-dependent flow fields. It provides a valuable
tool for the analysis of unsteady flows. Commonly
it is defined based on the flow map, analyzing the
separation of trajectories of nearby particles over a
finite-time span. This paper proposes a localized
definition of the FTLE using the Jacobian matrix
along a pathline as generator of the separation. The
localized FTLE (L-FTLE) definition makes only
use of flow properties along the pathline. A fast
computation algorithm is presented that efficiently
reuses FTLE values from previous time steps, fol-
lowing an idea similar to FastLIC. The properties
of L-FTLE are analyzed with focus on the sensitiv-

  

Source: Andrzejak, Artur - Konrad-Zuse-Zentrum für Informationstechnik Berlin

 

Collections: Computer Technologies and Information Sciences