The ESA/JAXA JEREMI (Japanese European Research Experiments on Marangoni Instabilities) Project

Lead Research Organisation: University of Strathclyde
Department Name: Mechanical and Aerospace Engineering

Abstract

The acronym JEREMI stands for "Japanese European Research Experiments on Marangoni Instabilities". This ambitious project is part of an agreement between the European Space Agency (ESA) and the Japanese Space Agency (JAXA). Started in 2001, it is now entering its final stage of preparation and is currently endorsed to fly on the International Space Station (ISS).
These experiments will be executed using the FPEF (Fluid Physics Experiment Facility) of JAXA, a multipurpose facility for the investigation of fluids in microgravity. Studies of such a kind are very relevant and useful as they make it possible to observe how some physical forces, interwoven or overshadowed in normal gravity conditions (essentially the fluid surface tension and its gradients), can have a crucial impact on the behaviour of liquids (leading to the so-called "Marangoni" or thermocapillary effect). Without the complications of gravity-driven convection flows on Earth, in particular, UK scientists want to test in space fundamental theories of three-dimensional laminar, oscillatory and turbulent flows generated by these forces, which can be applied, in principle, also in a variety of "terrestrial" circumstances.
More specifically, the JEREMI series of experiments is based on the so-called "liquid bridge", a drop of liquid with cylindrical free liquid-air interface held between two disks at different temperature. In space it is possible to form relatively large liquid bridges due to the absence of gravity, which would otherwise tend to deform the liquid-air interface and break the column of floating liquid. In microgravity conditions, the difference of temperature applied to the floating liquid produces buoyancy-free (purely surface-tension driven, i.e. Marangoni) convection. This type of flow is initially very regular, but it becomes oscillatory and three-dimensional if the applied temperature difference is increased beyond a given threshold. The project targets an improved understanding of this instability and the elaboration of possible means to control it by modifying the conditions at the liquid-air interface.
Another objective relates to the identification of the cause-and-effect relationships at the root of the so-called "Particle Accumulation Structures" (PAS). Very recently it has been discovered that, under the effect of Marangoni flow, solid particles initially distributed uniformly in a liquid bridge can demix spontaneously from the surrounding fluid and form three-dimensional aggregates. The resulting cluster or pattern formed by particles looks like a spatially extended "closed wire" or "circuit" (having the shape of a windmill with several blades). This fascinating structure has been observed to float inside the liquid and rotate in space with constant angular velocity, thereby giving the illusion of a freely-floating "rotating solid body".
An international team of scientists (from UK, Belgium, Austria, Spain and Japan) with different complementary backgrounds, expertise and perspectives, has been collaborating for more than 15 years to define precisely the set of space experiments to be executed to address the above topics. As the project is now entering its final stage, additional effort will be devoted to the elaboration of even more advanced mathematical and numerical tools to be used for the fine tuning of the experiment "input parameters" and for the interpretation of the flight results.
The objective of this project is to examine experimentally and model (theoretically and numerically) fundamental physical principles still poorly known, thereby generating "new knowledge" potentially applicable in a variety of fields, which range from mechanical, chemical and thermal engineering to materials science and from the manipulation of tiny particles in small-scale systems to problems with astrophysical scale. The project aligns with the research priorities listed in the UK National Strategy on Space Environments and Human Spaceflight.

Planned Impact

The project is anticipated to have a potential impact from different standpoints:
Fundamental science: This research will produce new and fundamental insights into the complex fluid-dynamic behaviour of surface-tension-driven (Marangoni) flows and the related dynamics of transported solid particles. There will be also significant advances in the class of mathematical sub-models required to deal with such phenomena (well known or partially of a prototypical nature as described in this proposal). Potential beneficiaries include researchers in academia.
Economic impact: The present project could lead to significant economic advantages in the long term. The engineering industry operating in the field of advanced materials (semiconductor, superconductor, magnetic materials and other transparent oxides) has been struggling for years to predict the effective conditions established inside the so-called Floating zone. The JEREMI project will increase our understanding of the typical fluid-dynamic instabilities produced by Marangoni flow and the related mechanisms for the transport of dispersed "impurities".
Supporting the recent inclusion of UK in the ESA's ELIPS and SciSpacE programme: The present project will strengthen the role of UK in space-research related activities. Indeed, it aligns perfectly with "the study of advanced materials in microgravity" theme, one of the two themes of the ELIPS programme, that UK is particularly interested in, as expressly stated by the UK science minister David Willetts (http://www.bbc.co.uk/news/science-environment-20421667).

Apart from the field of crystal-growth form the melt, the new knowledge being produced will contribute to improve the health of many other disciplines (in the long-term, this knowledge is likely to be directly or indirectly "useful" in many companion areas such as mechanical, chemical, thermal engineering and other materials science problems). Microgravity is indeed instrumental in allowing scientists to discern the effects of forces and mechanisms present in many natural phenomena and industrial processes that cannot be studied directly in normal gravity conditions because of the presence of the gravitational field created by our planet (that leads to buoyancy and sedimentation). The experiments performed in space and the related theoretical work performed by the UK team will lead to different benefits: better understanding of still poorly known physical mechanisms, new mathematical models and numerical tools for the analysis of such mechanisms.
Transdisciplinary knowledge exchange: It is intention of the UK PI to apply the results of the present research also to other (completely unrelated) fields such as atmospheric and geophysical sciences. The intrinsic interdisciplinary nature of the JEREMI project has indeed the potential for substantial impact across multiple research areas, which cover a wide range of spatial scales, going from the manipulation of tiny particles in small-scale systems up to very large-scale phenomena such as the accumulation of small dust particles in primordial solar nebulae (which finally leads to the formation of planets or proto-planets). Its high novelty will present a significant opportunity to develop over the medium-term a new knowledge-exchange community.

Publications

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