Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 27: Interfaces I

MM 27.2: Vortrag

Mittwoch, 25. März 2009, 11:45–12:00, IFW B

Phase-field modelling of foam microstructure evolution — •Frank Wendler, Eduard Stirner, and Britta Nestler — Institute of Computational Engineering, Karlsruhe University of Applied Sciences, Moltkestr. 30, 76133 Karlsruhe, Germany

Foam is a cellular materials with large variety of applications ranging from metal or polymer foams to cosmetics. After generation, a foam is a liquid with a complex rheological behaviour, dominated by surface free energy minimisation towards configurations of local equilibrium. We adapt a general multi phase-field model to describe this evolution step, important for the mechanical properties of a solidified foam material. Starting with a volume preserving Allen-Cahn model for incompressible dry foams with negligible liquid fraction (e.g. soap froth), a pressure dependant term is added to the functional of the free energy. This allows for the treatment of bubbles filled with a compressible gas. Assuming homogeneous pressures related to an equation of state a consistent model of boundary evolution can be given. The results approve that pressures within single bubbles are related to interface curvature according to the Young-Laplace equation. Simulations of bubble clusters and foam structures in 2D and 3D are presented, including the examination of pressure variations as a process step to optimize structure and accelerate equilibration. Finally, the treatment of wet foams with a non-negligible fraction of liquid, concentrated along the Plateau borders is given. Numerical evaluation of surface energies and dynamics show that it is not necessary to completely resolve the diffuse interface, which enables the simulation on larger length scales.