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Experiment/Payload Overview

Brief Summary

Simulation of Geophysical Fluid Flow under Microgravity (Geoflow) is an ESA investigation planned for the Fluid Science Laboratory (FSL) on the ISS. Geoflow will study thermal convection in the gap between two concentric rotating spheres to model Earth's liquid core.

Principal Investigator

Christoph Egbers, Ph.D., Brandenburg University of Technology, Cottbus, Germany

Co-Investigator(s)/Collaborator(s)

Philippe Beltrame, Ph.D., Max-Planck-Institut fur Physik Komplexer Systeme, Dresden, Germany

Pascal Chossat, Centre International Rencontres Mathematiques, Marseille, France

Frederik Feudel, University of Potsdam, Potsdam, Germany

Rainer Hollerbach, Ph.D., University of Leeds, Leeds, United Kingdom

Innocent Mutabazi, University of Le Havre, Le Havre, France

Laurette Tuckerman, Ph.D., Ecole Superieure de Physique et de Chimie Industrielles, Paris, France

Payload Developer

Brandenburg Technical University, Cottbus, Germany

Sponsoring Agency

European Space Agency (ESA)

Expeditions Assigned

|17|18|

Previous ISS Missions

Information Pending

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Experiment/Payload Description

Research Summary

• The Simulation of Geophysical Fluid Flow under Microgravity (Geoflow) experiment will investigate the flow in a viscous incompressible fluid (silicone oil) held between two concentric spheres. A central force field is introduced by applying a high voltage difference (10 kV) between the two spheres. Maintaining the inner sphere at a higher temperature than the outer sphere also creates a temperature gradient (0 to 10 degrees K).



• The spheres can rotate (rotation rate between 0 and 2 Hz). This geometrical configuration can be seen as a representation of the Earth's liquid core, where the role of gravity is played by the central electric field. These experiments require a weightless environment in order to turn off the unidirectional effect of gravity on Earth.

Description

Simulation of Geophysical Fluid Flow under Microgravity (Geoflow) will investigate the flow of a viscous incompressible fluid between two concentric spheres, rotating about a common axis, under the influence of a simulated central force field. This is of importance for astrophysical and geophysical problems, like global scale flow in the atmosphere, the oceans, and in the liquid nucleus of planets. There is also an applied interest in this work: the electro-hydrodynamic (EHD) force that simulates the central gravity field may find applications in high-performance heat exchangers, and in the study of electro-viscous phenomena.

Geoflow experiment parameters are rotation rate, high voltage and temperature difference. The thermal convection will be observed between the two spheres. The temperature distribution will be measured by using Wollaston Shearing Interferometry, and additional optical diagnostics may also be used (Schlieren or shadowgraphy).

Geoflow will determine the following:

• The stability of the basic states and its transitions will be studied for both the non-rotating and rotating situations.


• The characteristics of the convection flows and in particular their symmetries will be determined.


• The critical Rayleigh number which denotes linear stability and marks the onset of thermal convection should be detected.


• The stability diagram for the different states should be measured and the occurrence of multi-stability will be investigated.


• The energy transport from the inner sphere to the outer sphere should be estimated.The characteristic wave numbers should be determined.


• Time dependent up to chaotic behavior will be detected; drift velocities and non-linear dynamics such as mode interactions will be analyzed.

As a result, a detailed description of the transition to turbulence and the transition scenarios to chaos should be obtained. Numerical simulations and comparisons of Geoflow with theoretical predictions for the flow pattern bifurcating from trivial state will be conducted, as well as a comparison with theoretical work on the flow in the Earth's interior.

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Applications

Space Applications

Information Pending

Earth Applications

Information Pending

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Operations

Operational Requirements

Information Pending

Operational Protocols

The crew has to insert the Geoflow experiment container in the FSL, and then remove it at the end of the experiment. The experiment is controlled from the ground. The crew only has to change the backup tapes as needed (insert a new one when the previous one is full).

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Results/More Information

Information Pending

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Related Web Sites

Geoflow Homepage

Columbus Mission - European Experiment Programme

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Publications

Results Publications

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Related Publications

• Beltrame P, Egbers C, Hollerbach R. The Geoflow-experiment on ISS (Part III): Bifurcation analysis. Advances in Space Research. ;32(2):190 - 197. 2003
• Travnikov V, Egbers C, Hollerbach R. The Geoflow-experiment on ISS (Part II): Numerical simulation. Advances in Space Research. ;32(2):181-189. 2003
• Egbers C, Beyer W, Bonhage A, Hollerbach R, Beltrame P. The Geoflow-experiment on ISS (Part I): Experimental preparation and design of laboratory testing hardware. Advances in Space Research. ;32(2):171-180. 2003
• Futterer B, Brucks A, Hollerbach R, Egbers Ch. Thermal blob convection in spherical shells. Journal of Heat Mass Transfer. ;50(19-20):4079 - 4088. 2007
• Futterer B, Gellert M, von Larcher Th, Egbers C. Thermal Convection In Rotating Spherical Shells: An Experimental And Numerical Approach Within Geoflow. Acta Astronautica. ;(In Review). 2007

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Images

Geoflow concept: concept diagram of the Geoflow experiment. Image courtesy of ESA.
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Geoflow fluid cell assembly: core of the experiment. Inner sphere is just visible inside outer glass sphere. Image courtesy of ESA.
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Geoflow experiment container: Geoflow fluid cell assembly, optical elements and other sub-systems integrated in the experiment container for FSL. Image courtesy of ESA.
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Geoflow calculations: typical Geoflow numerical simulation result for temperature field and velocity field. Image courtesy of ESA.
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This is the first image from the European Space Agency sponsored Geoflow experiment. In this interferogram are fringe patterns ("bulls-eye") that scientists use to calculate the temperature field. Image courtesy of ESA.
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This interferogram is used to calculate the temperature field analyzing the "bulls-eye" (fringe) patterns. Geoflow studies thermally driven rotating fluids which can be used in modeling the convection of the Earth. Image courtesy of ESA.
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NASA Image: ISS018E006455 - Astronaut Greg Chamitoff, Expedition 18 flight engineer, installs a Geoflow experiment container in the Columbus laboratory of the International Space Station.
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Information Provided and Updated by the ISS Program Scientist's Office