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DY: Dynamik und Statistische Physik

DY 38: Fluid Dynamics

DY 38.4: Vortrag

Mittwoch, 29. März 2006, 17:30–17:45, SCH 251

Shear flow in freely suspended liquid crystal films induced by elastic stress — •Alexey eremin, christian bohley, and ralf stannarius — Otto-von-Guericke-Universität Magdeburg, Institut für Experimentalphysik

Hydrodynamic phenomena observed in liquid crystalline materials are far more complex than those in conventional Newtonian fluids. The reasons lies in the coupling of macroscopic translational motions to inner degrees of freedom, created by broken symmetries. We present an experimental and theoretical study of vortex flow in freely suspended smectic films that is induced entirely by elastic distortions of the orientational director field. By means of an external electric field, a periodically deformed director field is prepared, which, after the field is switched off, relaxed into a homogeneous state. Macroscopic flow is induced by this director reorientation. It is visualized by tracer particles imposed on the film surface. We discuss experimental results and theoretical models developed for different configurations of the director field. It is shown that the presence or absence of a central topological defect has essential influence on the relaxation dynamics of flow and director fields. From a quantitative analysis, shear viscosities of the material can be accessed.