Estimates on diagnostic methods for investigations of thermal convection between spherical shells in space

Abstract

Thermal convection in a spherical shell represents an important model in fluid dynamics and geophysics. Investigations on thermal convective instabilities occurring in the spherical gap flow under terrestrial conditions are of basic importance, especially for the understanding of symmetry-breaking bifurcations during the transition to chaos. Microgravity experiments on thermal convection with a simulated central force field are important for the understanding of large-scale geophysical motions such as the convective transport phenomena in the Earth's liquid outer core. More than one diagnostic tool is needed to examine and characterize the different flow types. Flow visualization, Wollaston shearing interferometry and laser Doppler velocimetry should be available for space experiments. This report summarizes concurrent theoretical, numerical and experimental studies for the preparation of a Get Away Special (Shuttle) experiment as well as a Space Station experiment inside the Fluid Science Laboratory. The special experimental device for investigations of supercritical and turbulent thermal convection in spherical shells under a central force field with respect to geophysical simulations is called an electrohydrodynamic container. A central symmetric force field similar to the gravity field acting on planets can be produced using the effect of the dielectrophoretic force field by applying a high-voltage potential difference to the inner and outer sphere.