Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: POSTERS Driven Soft Matter

CPP 20.28: Poster

Mittwoch, 27. Februar 2008, 16:00–18:30, Poster A

Viscoelastic Instabilities — •Christian Wagner — Technische Physik, Universität des Saarlandes, 66123 Saarbrücken

Viscoelastic liquids are characterized by a complex viscosity with a dissipative and an elastic contribution. Similar to simple Newtonian liquids, above a critical threshold, one can observe a transition from laminar to complex flow situations. But other than in Newtonian liquids, the threshold might occur at Reynolds numbers Re << 1. The critical condition of the instability is mainly determined by the so called Weisenberg Number, the ratio of the flow rate to the characteristic relaxation time of the liquid. This leads to completely new instability mechanisms, like e.g. the subcritical formation of double whirl patterns in Taylor Couette flow, the occurrence of turbulent like flow in planar Couette flow at vanishing Reynolds numbers or the transition to elastic turbulence in Poiseuille flow that can lead to melt fracture, a severe problem in fiber spinning processes. We present a general introduction into the problem of elastic instabilities and present experimental and theoretical results on elastic instabilities in Poiseuille flow.