Releasing trapped Taylor bubbles via centrifugation and inclination
arxiv(2024)
摘要
In confined systems, the entrapment of a gas volume with an equivalent
spherical diameter greater than the dimension of the channel can form extended
bubbles that obstruct fluid circuits and compromise performance. Notably, in
sealed vertical tubes, buoyant long bubbles – called Taylor bubbles – cannot
rise if the inner tube radius is below a critical value near the capillary
length. This critical threshold for steady ascent is determined by geometric
constraints related to matching the upper cap shape with the lubricating film
in the elongated part of the bubble. Developing strategies to overcome this
threshold and release stuck bubbles is essential for applications involving
narrow liquid channels. Effective strategies involve modifying matching
conditions with an external force field to facilitate bubble ascent. However,
it's unclear how changes in acceleration conditions affect the motion onset of
buoyancy-driven long bubbles. This study investigates the mobility of elongated
bubbles in sealed tubes with an inner radius near the critical value inhibiting
bubble motion in a vertical setting. Two strategies are explored to tune bubble
motion, leveraging variations in axial and transversal accelerations: tube
rotation around its axis and tube inclination relative to gravity. By revising
the geometrical constraints of the simple vertical setting, the study predicts
new thresholds based on rotational speed and tilt angle, respectively,
providing forecasts for the bubble rising velocity under modified apparent
gravity. Experimental measurements of motion threshold and rising velocity
compare well with theoretical developments, thus suggesting practical
approaches to control and tune bubble motion in confined environments.
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