Studies of Floating Liquid Zones in Simulated Zero Gravity

Abstract

Floating liquid zones of water/ethanol solutions were suspended between glass tubes inside mineral oil. When the densities of the two liquids were equal, there was no net gravitational force acting on the interface between them. The shape stability of this interface was studied under conditions of density imbalance and end‐member rotation. Cylindrical, conical, and spherical zone shapes were investigated. Our results show that the generally accepted Heywang criterion for the stability of cylindrical liquid zones is no longer valid under reduced gravitational conditions. The convective flow patterns in the zone due to rotation have been studied in detail and show the existence of distinctly different flow regimes. In all cases the outer liquid rotated more slowly than the end faces and so resulted in Taylor‐Proudman‐type axial flow. However the liquid near the rotation axis behaved quite differently; for equal isorotation of the end faces, a central core of liquid rotated as a solid core at the same rate as the imposed velocity, while for equal counterrotation, the central core of liquid showed a zero angular velocity. The implications of these studies for crystal growth are considered.