Regensburg 2004 – wissenschaftliches Programm

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SYPF: Physics of Foams

SYPF 1: Foams I

SYPF 1.1: Hauptvortrag

Mittwoch, 10. März 2004, 14:00–14:30, H16

The foam/emulsion analogy in structure and drainage — •Stefan Hutzler, Nicolas Peron, Denis Weaire, and Wiebke Drenckhan — Physics Department, Trinity College Dublin, Ireland

In recent years the study of the physics of foams has advanced across a wide front. Often the analysis of a property will begin with the assertion that the same description applies equally well to an emulsion. However, this is rarely tested.

We have therefore revisited some of the key experiments, using a water-silicone oil emulsion system (stabilised by surfactants) of similar scale to familiar foam systems. Here we present illustrations of several ordered structures in cylindrical tubes, essentially identical to those observed in foams.

We have also performed the common foam experiment of “forced drainage” on these emulsions, i.e. adding surfactant solution from the top at constant flow rates. These experiments suggest that drainage is of the Poiseuille type flow of liquid past the drops.

At high flow rates the drops exhibit oscillations within the emulsion, eventually leading to a break-up of the arrangement. This differs from the behaviour of foams, where varies types of convective instabilities set in, once a critical flow rate, dependent on bubble size and geometry, is exceeded.