Jens-Kasten.de

Lagrangian Feature Extraction of the Cylinder Wake

We extract Lagrangian features in the 2-D von-Kármán vortex street behind a circular cylinder.  The distance of neighboring fluid particles is monitored with forward and backward time evolution over two shedding periods. The height of the grey surface represents the maximum of the logarithm of these distances (FTLE in Kasten et al. VMV 2009). Red coloring indicates regions of particle divergence in forward time. Blue regions show convergence.  The intersection of both curves marks Lagrangian saddle points (Haller 2001 Phys. D). The direction of the flow field is indicated by lines on the surface. Thus, the mixing of the von-Kármán vortex street is characterized by the Lagrangian saddle points, their attractive and separating invariant manifold "arms" mark domains of particle attraction and separation. Our project has been supported by the Deutsche Forschungsgemeinschaft (DFG) via the Collaborative Research Center (SFB 557) "Control of complex turbulent shear flows" and the Emmy Noether program, and the U.S. National Science Foundation (US NSF). We acknowledge support of the Amira developer team at ZIB.

 

Bibtex: 
@ARTICLE{Kasten2010b, 
  Author = {Jens Kasten and Christoph Petz and Ingrid Hotz and Gilead Tadmor 
            and Bernd R Noack and Hans-Christian Hege}, 
  title = {Lagrangian Feature Extraction of the Cylinder Wake}, 
  journal = {Physics of Fluids},   
  year = {2010},
  volume = {22},
  pages = {091108 - 1}, 
  number = {9},
  note = {Gallery of Fluid Motion Award 2009},
}