Seminar Room 1, Newton Institute
This work explores connections between two large fields of current research: the instability of fluid/fluid interfaces known as Saffman-Taylor fingering, and the opening of voids in solid materials known as crack propagation. A liquid foam in a Hele-Shaw cell is a unique model system with characteristics of both cases: The dynamics of air injected into the foam can be described by effective-medium theory as finger propagation, yet the detailed information about position and shape of individual bubbles makes a description in terms of solid microstructural changes possible. The accessibility of the microstructure (at the single-bubble level) allows for direct observation of defect dynamics and neighbor changes. Transitions akin to brittle/ductile crack behavior are also observed.