Strain and liquid content of sheared stretching foams: a model for dynamic dilatancy

B. Embley, P. Grassia

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

In drainage experiments for liquid–gas foams, a sufficiently large liquid flow rate results in a downwards convection of bubbles. This 'wet', downwards-convecting region of foam can coexist with stationary 'dry' regions or with 'dry' regions that convect upwards. A possible explanation of this phenomenon is dilatancy. We introduce and develop a model that considers the dynamic dilatancy of a foam via force balances on a continuously sheared sample with a finite liquid fraction. Using microstructural information for the strain of typical foam structures (e.g. Kelvin and Weaire–Phelan foams) and the notion of stretching Plateau borders (i.e. foam channels) within a non-uniform bubble velocity field, the model can estimate the liquid content within a convective roll. Alternatively liquid content can be obtained via previously established relations between applied shear rate and foam osmotic pressure. The continuously sheared, downwards-convecting portion of foam is predicted to subsist at higher liquid content than an adjacent, unyielded, upwards-convecting portion of foam. Sustainable liquid content variations in the dynamic dilatancy model are comparable to or greater than those associated with static foam dilatancy.
LanguageEnglish
Pages24-32
Number of pages9
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Volume344
Issue number1-3
Early online date26 Feb 2009
DOIs
Publication statusPublished - 20 Jul 2009
Event7th Eufoam Conference - Noordwijk, Netherlands
Duration: 8 Jul 200810 Jul 2008

Fingerprint

foams
Stretching
Foams
Liquids
liquids
bubbles
osmosis
liquid flow
drainage
Bubbles (in fluids)
borders
dynamic models
Shear deformation
Drainage
Dynamic models
plateaus
convection
flow velocity
velocity distribution
Gases

Keywords

  • foam drainage
  • dilatancy
  • convective instability
  • simple shear

Cite this

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title = "Strain and liquid content of sheared stretching foams: a model for dynamic dilatancy",
abstract = "In drainage experiments for liquid–gas foams, a sufficiently large liquid flow rate results in a downwards convection of bubbles. This 'wet', downwards-convecting region of foam can coexist with stationary 'dry' regions or with 'dry' regions that convect upwards. A possible explanation of this phenomenon is dilatancy. We introduce and develop a model that considers the dynamic dilatancy of a foam via force balances on a continuously sheared sample with a finite liquid fraction. Using microstructural information for the strain of typical foam structures (e.g. Kelvin and Weaire–Phelan foams) and the notion of stretching Plateau borders (i.e. foam channels) within a non-uniform bubble velocity field, the model can estimate the liquid content within a convective roll. Alternatively liquid content can be obtained via previously established relations between applied shear rate and foam osmotic pressure. The continuously sheared, downwards-convecting portion of foam is predicted to subsist at higher liquid content than an adjacent, unyielded, upwards-convecting portion of foam. Sustainable liquid content variations in the dynamic dilatancy model are comparable to or greater than those associated with static foam dilatancy.",
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Strain and liquid content of sheared stretching foams : a model for dynamic dilatancy. / Embley, B.; Grassia, P.

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, Vol. 344, No. 1-3, 20.07.2009, p. 24-32.

Research output: Contribution to journalArticle

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