Modelling froth dynamics; persistence measures

Citation
Hj. Ruskin et al., Modelling froth dynamics; persistence measures, PHYSICA A, 293(3-4), 2001, pp. 315-323
Citations number
29
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
PHYSICA A
ISSN journal
0378-4371 → ACNP
Volume
293
Issue
3-4
Year of publication
2001
Pages
315 - 323
Database
ISI
SICI code
0378-4371(20010415)293:3-4<315:MFDPM>2.0.ZU;2-2
Abstract
The soap froth provides an idealised example of a cellular structure, which evolves or coarsens over laboratory time-scales and for which topological measures appear to provide an intuitive characterisation. However, froth is an intrinsically non-equilibrium system, and topological measures are not universally applicable to such processes. Recently, persistence has been pr oposed as a more general probe of non-equilibrium dynamics, where the froth is viewed as a two-phase system through construction of a virtual phase. W e use a direct simulation method to investigate persistence fur random 2-D (Voronoi) and hexagonal froths of size up to 2500 bubbles. We find that sim ulation results are qualitatively similar to those of experiment, with the normalised average area, (A*(t)/A(0)), of persistent regions within a bubbl e at time t approaching an equilibrium Value for a range of volume (or samp ling) fraction values, phi, for the Voronoi froth. The case for the hexagon al is less clear, since exclusion of the defect (or defects) from the virtu al phase leads to rapid decline in the average area of persistent bubbles. Simulation times required are very long, however, and evolution is slow for long-term survivors. Consequently, persistent behaviour is not demonstrate d satisfactorily for the fraction of survivors, N*(t)/N(t), in a random sys tem of this size, although for the hexagonal with one or more seeded defect s, there is some indication that decay depends on phi, for some colouring p atterns. However, limiting slope values are probably not established. (C) 2 001 Elsevier Science B.V. All rights reserved.