Sheet-like and plume-like thermal flow in a spherical convection experiment performed under microgravity
OPEN ACCESS
Loading...
Author / Creator
Date
2013-11
Publication Type
Journal Article
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
We introduce, in spherical geometry, experiments on electro-hydrodynamic driven Rayleigh–Bénard convection that have been performed for both temperature-independent (‘GeoFlow I’) and temperature-dependent fluid viscosity properties (‘GeoFlow II’) with a measured viscosity contrast up to 1.5. To set up a self-gravitating force field, we use a high-voltage potential between the inner and outer boundaries and a dielectric insulating liquid; the experiments were performed under microgravity conditions on the International Space Station. We further run numerical simulations in three-dimensional spherical geometry to reproduce the results obtained in the ‘GeoFlow’ experiments. We use Wollaston prism shearing interferometry for flow visualization – an optical method producing fringe pattern images. The flow patterns differ between our two experiments. In ‘GeoFlow I’, we see a sheet-like thermal flow. In this case convection patterns have been successfully reproduced by three-dimensional numerical simulations using two different and independently developed codes. In contrast, in ‘GeoFlow II’, we obtain plume-like structures. Interestingly, numerical simulations do not yield this type of solution for the low viscosity contrast realized in the experiment. However, using a viscosity contrast of two orders of magnitude or higher, we can reproduce the patterns obtained in the ‘GeoFlow II’ experiment, from which we conclude that nonlinear effects shift the effective viscosity ratio.
Permanent link
Publication status
published
External links
Editor
Book title
Journal / series
Volume
735
Pages / Article No.
647 - 683
Publisher
Cambridge University Press
Event
Edition / version
Methods
Geographic location
Date collected
Date created
Subject
Bénard convection; Geophysical and geological flows; Nonlinear dynamical systems
Organisational unit
Notes
Received 8 February 2013, Revised 21 August 2013, Accepted 19 September 2013, Published online 29 October 2013. It was possible to publish this article open access thanks to a Swiss National Licence with the publisher