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The objective of the FOAM (Foam Optics And Mechanics) flight experiment
is to study the characteristics of wet foams in the absence of gravity.
The microgravity environment on the ISS will eliminate drainage
of liquid out of the wet foams at high liquid contents. This experiment
is a joint collaborative project between the European Space Agency
(ESA) and NASA. As part of the ISS Non-Exploration Program, Professor
Douglas Durian, University of Pennsylvania, Department of Physics,
participates as the U.S. principal investigator, and is supported
by NASA. Professor Dominique Langevin of the University of Paris
South (UPS) leads the flight project. As part of the international
science team, ESA also supports several additional scientists from
Germany, Ireland, France, Belgium and Sweden, mostly from universities.
ESA is currently designing the FOAM flight hardware with the lead contractor
ASTRIUM (Germany). The FOAM hardware is being integrated into the Microgravity
Science Glovebox (MSG) facility. The FOAM Preliminary Design Review
(PDR) was held at the contractor’s facility in Germany and successfully
completed during the 3rd week of December 2006. As recently proposed
at the PDR by Prof. Durian, ESA and the European contractors are planning
to integrate Speckle Visibility Spectroscopy, a newly developed technique
by Professor Durian, to further elucidate how foam structures evolve
over time in a microgravity environment. The flight module is expected
to be delivered in late 2008. The tentative flight date is July 2009.
- Science Objectives: To exploit microgravity
conditions to quantify and elucidate the unusual elastic character
of foam structure and dynamics. To observe how the foam melts
into a simple viscous liquid as a function of both increasing
liquid content and shear strain rate.
- Relevance/Impact: The proposed flight research
generate valuable fundamental guidance for the development of
materials with more desirable rheology and better stability. On
board Rheometry and light scattering techniques will provide the
rheology and coarsening in terms of microscopic structure and
dynamics.
- Justification for Microgravity: Microgravity
environment will eliminate drainage of liquid out of the wet foams
at higher liquid content.
- Joint collaborative project between NASA and
ESA.
European P.I.s: Langevin , Saint-Jalmes, Adler (France,), Vanderwalle
(Belgium), Waiere (Ireland), Odenbach, Banhardtn (Germany), Kronberg
(Sweden)
Objective
To exploit rheological and multiple-light
scattering techniques, and ultimately microgravity conditions, in
order to quantify and elucidate the unusual elastic character of
foams in terms of their underlying microscopic structure and dynamics.
Special interest is in determining how this elastic character vanishes,
i.e., how the foam melts into a simple viscous liquid as a function
of both increasing liquid content and shear strain rate.
Description
The unusual elastic character of foams will
be quantified macroscopically by measurement of the shear stress
as a function of static shear strain, shear strain rate, and time
following a step strain; such data will be analyzed in terms of
a yield stress, a static shear modulus, and dynamical time scales.
Microscopic information about bubble packing and rearrangement
dynamics, from which these macroscopic non-Newtonian properties
presumably arise, will be obtained non-invasively by novel multiple-light
scattering diagnostics such as diffusing-wave spectroscopy (DWS).
Quantitative trends with materials parameters, such as average
bubble size, and liquid content, will be sought in order to elucidate
the fundamental connection between the microscopic structure and
dynamics and the macroscopic rheology.
Significance
The utility and fascination of foams are derived
largely from the surprising fact that they have a solid-like elastic
character in spite of being mostly gas with a few percent volume
fraction of liquid, but can nevertheless flow under shear. The physical
origin of such unusual rheology in terms of microscopic structure
and dynamics is poorly understood. The flight experiment promises
important new insight into these issues, and could also have significant
consequences for our understanding of flow in other dense randomly-packed
systems such as emulsions, colloidal suspensions, slurries, bubbly
liquids, and granular materials. Furthermore, all foam applications
are empirically based and the proposed research may generate valuable
fundamental guidance for the development of materials with more
desirable rheology and better stability.
The FOAM is dedicated to the study of aqueous and
non-aqueous foams in the microgravity environment onboard the International
Space Station (ISS). In particular, "wet" foams which
cannot be stabilized on earth because of drainage will be investigated
under microgravity conditions.
The Foam Experiment Assembly (FEA) will provide the
possibility to perform three different types ofexperiments:
• Rheometry, to quantify and elucidate the visco-elastic character
of foams in terms of their underlyingmicroscopic structures and dynamics
• Drainage, to better describe the hydrodynamics of foams at
high liquid fraction, and thus to advance thedevelopment of simulation
tools
• Stability, to define physico-chemical aspects of unstable foams.
To carry out these experiments, the FEA, hosted by
the Microgravity Science Glovebox (MSG) will have 5 functional units:
• Stability, Drainage and Rheometry Insert (SDRI)
• Electrical Subsystem (ESS FEME)
• Gas Mixing Unit (GMU)
• Solution Cartridge
• Liquid-Gas Cartridge
Instrument Description
The FOAM Experiment Assembly (FEA) designed to perform
FOAM experiments can be broken down into two major scientific instrumentation
assembly, together known as SDRI (Stability Drainage Rheometry Insert):
In the SDRI:
(1) The Stability experiment Unit (STU) including the following subunits:
- Foam generation subunits (translation grid mechanism)
- Two Stability experiment cells
- Scientific diagnostic devices
- STU internal structure
(2) The Drainage rheometry experiment unit (DRU)
including the following subunits:
- Foam generation subunit (close loop)
- Rheometer compressor
- Drainage Rheometry experiment cell
- Scientific diagnostic devices
- DRU internal structure |
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Wet Foam
and Drainage |
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Wet Foam
and Drainage |
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FOAM Experiment
Assembly (FEA) in MSG |
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Stability
Drainage Rheometry Integration
(SDRI) |
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