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DY: Fachverband Dynamik und Statistische Physik

DY 13: Fluid Dynamics and Turbulence I

DY 13.4: Talk

Tuesday, March 15, 2011, 11:15–11:30, ZEU 118

Nematic electroconvection under time-reversed excitation — •Dirk Pietschmann, Thomas John, and Ralf Stannarius — Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg

We investigate experimentally nematic electrohydrodynamic convection (EHC) as a paradigm for a dissipative pattern formation system. We construct periodical waveforms which are reversed in time (forward and backward) to the same control parameter amplitudes. The standard model of EHC is described by a set of two linear differential equations (Carr-Helfrich mechanism). Because of additional symmetries in the equations, EHC belongs to the special class of dynamical systems, in which no differences in the threshold voltages for forward and backward excitation are expected. But our experimental investigations shows in certain parameter regions different threshold voltages for forward and backward excitations. This can not be explained with the standard model for electrohydrodynamic convection. Traveling rolls and localized structures (worms) are observed in the transition regime between the thresholds.

D. Pietschmann, Th. John and R. Stannarius, Phys. Rev. E 82, 046215 (2010).