Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Local origin of the visco-elasticity of a millimetric elementary foam   Liquid foam exhibits surprisingly high viscosity, higher than each of its
phases. This dissipation enhancement has been rationalized by invoking either a
geometrical confinement of the shear in the liquid phase, or the influence of
the interface viscosity. However, a precise localization of the dissipation,
and its mechanism, at the bubble scale is still lacking. To this aim, we
simultaneously monitored the evolution of the local flow velocity, film
thickness and surface tension of a five films assembly, induced by different
controlled deformations. These measurements allow us to build local
constitutive relations for this foam elementary brick. We first show that, for
our millimetric foam films, the main part of the film has a purely elastic,
reversible behavior, thus ruling out the interface viscosity to explain the
observed dissipation. We then highlight a generic frustration at the menisci,
controlling the interface transfer between neighbor films and resulting in the
localization of a bulk shear flow close to the menisci. A model accounting for
surfactant transport in these small sheared regions is developed. It is in good
agreement with the experiment, and demonstrate that most of the dissipation is
localized in these domains. The length of these sheared regions, determined by
the physico-chemical properties of the solution, sets a transition between a
large bubble regime in which the films are mainly stretched and compressed, and
a small bubble regime in which they are sheared. Finally, we discuss the
parameter range where a model of foam viscosity could be built on the basis of
these local results.

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The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math