Unexpected spatial distribution of bubble rearrangements in coarsening foams

Abstract

Foams are ideal model systems to study stress-driven dynamics, as stress-imbalances within the system are continuously generated by the coarsening process, which unlike thermal fluctuations, can be conveniently quantified by optical means. However, the high turbidity of foams generally hinders the detailed study of the temporal and spatial distribution of rearrangement events, such that definite assessments regarding their contribution to the overall dynamics could not be made so far. In this paper, we use novel light scattering techniques to measure the frequency and position of events within a large sample volume. As recently reported (A. S. Gittings and D. J. Durian, Phys. Rev. E, 2008, 78, 066313), we find that the foam dynamics is determined by two distinct processes: intermittent bubble rearrangements of finite duration and a spatially homogeneous quasicontinuous process. Our experiments show that the convolution of these two processes determines the age-dependence of the mean dynamics, such that relations between intermittent rearrangements and coarsening process can not be established by considering means. By contrast the use of the recently introduced photon correlation imaging technique (A. Duri, D. A. Sessoms, V. Trappe, and L. Cipelletti, Phys. Rev. Lett., 2009, 102, 085702) enables us to assess that the event frequency is directly determined by the strain-rate imposed by the coarsening process. Surprisingly, we also find that, although the distribution of successive events in time is consistent with a random process, the spatial distribution of successive events is not random: rearrangements are more likely to occur within a recently rearranged zone. This implies that a topological rearrangement is likely to lead to an unstable configuration, such that a small amount of coarsening-induced strain is sufficient to trigger another event.

References in corpus (9)

• Rheology of Soft Glassy Materials
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• Time Resolved Correlation measurements of temporally heterogeneous dynamics
• Quantitative modeling of laser speckle imaging
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• Statistics of bubble rearrangement dynamics in a coarsening foam
• Unexpected spatial distribution of bubble rearrangements in coarsening foams

Cited by in corpus (8)

• Improved diffusing wave spectroscopy based on the automatized determination of the optical transport and absorption mean free path
• Unexpected spatial distribution of bubble rearrangements in coarsening foams
• Spatially-resolved measurements of micro-deformations in granular materials using DWS
• Avalanche statistics during coarsening dynamics
• Diffusive and arrested-like dynamics in currency exchange markets
• Uncovering the dynamic precursors to motor-driven contraction of active gels
• Multiple dynamic regimes in a coarsening foam
• Multispeckle diffusing wave spectroscopy as a tool to study heterogeneous mechanical behavior in soft solids