Microgravity bubble migration in rotating flows
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Engineering topics
Publications and source records attributed to Ruggles, J. S..
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The migration of bubbles or drops in a rotating liquid-filled sphere was observed under a variety of experimental conditions, and the trajectory, final equilibrium position, and shape were compared with results of analysis. It was found that small migrating bubbles or drops were spherical and, under the quasi-steady conditions employed, behaved in a predictable manner. Large migrating bubbles were nonspherical yet still behaved predictably except when close to the sphere wall. At low rotation rates, the final equilibrium position was offset from the rotation axis and stationary in the rotating liquid relative to a laboratory (inertial) reference frame. One of the bubble migration experiments was accomplished in the near-free-fall environment provided by the NASA KC-135 flight program. At higher rotation rates and under zero gravity conditions where the rotation axis is the final equilibrium position, the shape was reasonably predictable.
The NASA KC-135 microgravity-environment aircraft was used to gather experimental data on the migration of bubbles in rotating liquid fields under reduced gravity conditions. The data thus obtained were compared to those of an analysis for the prediction of fluid particle trajectories in the presence of both gravitational and rotational fields at the limit of quasi-steady creeping flow. Reasonable agreement with experimental results was achieved, despite the large size of the bubbles, their close proximity to a bounding surface over significant portions of their migration time, and their rather nonspherical geometry.