Dresden 2006 – wissenschaftliches Programm

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SYSS: Structure Formation and Self-Organization in non-equilibrium Systems

SYSS 1: Structure Formation and Self-Organization in non-equilibrium Systems I

SYSS 1.4: Vortrag

Donnerstag, 30. März 2006, 10:15–10:30, BAR Sch\"o

Hexaroll chaos in inclined layer convection — •Will Brunner1, Jonathan McCoy2, Werner Pesch3, and Eberhard Bodenschatz1,21Max Planck Institute for Dynamics and Self-Organization, Goettingen — 2LASSP, Department of Physics, Cornell University — 3Physikalisches Institut, Universitaet Bayreuth

We present results from experiments in thermal convection with the aim of studying defect mediated turbulence. We induce a defect turbulent state by tilting non-Boussinesq convection 5 degrees from horizontal. This breaks the symmetry of the hexagonal pattern, producing a pattern that resembles hexarolls found in cylindrical rotating convection. We find a new type of defect complexes in addition to the expected penta-hepta defects (PHDs), where a dislocation of one sign is found in one hexagonal mode and one of opposite sign is nearby in another mode. These new defect complexes, which we term same-mode complexes (SMCs) consist of two dislocations of opposite sign in the same mode. SMCs can self-annihilate, unlike PHDs which can only annihilate pairwise. This self-annihilation gives rise to a term in the annihilation rate law that is proportional to the number of defects present. We conclude that mass action is a robust concept for dealing with reaction rates in defect turbulence, and propose that SMCs may be present in other systems where an anomalous linear annihilation rate is seen.

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