Fluid surface behavior in low gravity. Center discretionary fund no. 8321
Abstract
Measurements of rotating equilibrium bubble shapes in the lowgravity environment of a freefalling aircraft are presented. Emphasis is placed on bubbles which intersect the container boundaries. These data are compared with theoretical profiles derived from Laplace's formula and are in good agreement with the measurements. Two types of instability are explored. The first occurs when the baffle spacing is too large for the bubble to intersect both the top and bottom boundaries. The second occurs when the hydrostatic pressure beneath a displaced free surface does not compensate for pressure change due to capillary forces. The interface shape depends on the contact angle, the radius of intersection with container, and the parameter F which is a measure of the relative importance of centrifugal force to surface tension. For isolated bubbles, F has a maximum value of 1/2. A further increase in F causes the bubble to break contact with the axis of rotation. For large values of F, the bubble becomes more cylindrical and the capillary rise occurs over a thinner layer so that the small radius of curvature can generate enough pressure drop to balance the increased hydrostatic contribution.
 Publication:

NASA Marshall Space Flight Center Report
 Pub Date:
 June 1985
 Bibcode:
 1985msfc.reptQ....L
 Keywords:

 Bubbles;
 Fluid Mechanics;
 Gravitation;
 Reduced Gravity;
 Shapes;
 Stability;
 Laplace Equation;
 Pressure Reduction;
 Rotation;
 Fluid Mechanics and Heat Transfer