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SUMMARY:Transition to turbulence and turbulent bifurcation in a von Karman
  flow - Daviaud\, F (CEA/Saclay)
DTSTART:20080911T094000Z
DTEND:20080911T100000Z
UID:TALK13372@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:We study the transition from laminar flow to fully developed t
 urbulence in a von Karman flow (Re from 50 to 106). The flow undergoes a c
 lassical succession of bifurcations driven by the destabilization of the a
 zimuthal shear-layer. We observe that the transition to turbulence is glob
 ally supercritical: the kinetic energy of the velocity fluctuations can be
  used as a single order parameter to characterize the transition. We also 
 measure the dissipation through the torque injected in the flow. For high 
 Reynolds numbers\, the mean flow presents multiple solutions: the canonica
 l symmetric solution becomes marginally unstable towards a flow which brea
 ks the basic Rπ-symmetry. The global bifurcation between these states is 
 highly subcritical and the system thus keeps a memory of its history. The 
 transition recalls low-dimension dynamical system transitions and exhibits
  slow dynamics and peculiar statistics. \n\nReferences F. Ravelet et al.\,
  J. Fluid Mech. 601\, 339 (2008) F. Ravelet et al.\, Phys. Rev. Lett. 93\,
  164501 (2004) 
LOCATION:Seminar Room 1\, Newton Institute
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