Flows around confined bubbles and their importance in triggering pinch-off
Volkert van Steijn1, Chris R Kleijn, Michiel T Kreutzer
1Multiscale Physics, Delft University of Technology, Prins Berhardlaan 6, 2628 BW Delft, The Netherlands.
Physical Review Letters
|April 7, 2010
Summary
Gas thread breakup in liquid streams is driven by internal liquid flow, not instability. This faster-than-expected flow, caused by curvature differences, enables precise prediction of pinch-off moments.
Area of Science:
- Fluid dynamics
- Microfluidics
- Multiphase flow
Background:
- Understanding bubble formation and breakup is crucial in microfluidic devices.
- Previous models often relied on Plateau-Rayleigh instability for gas thread breakup.
- The dynamics of confined gas threads in cross-flowing liquids require further investigation.
Purpose of the Study:
- To investigate the primary mechanism driving the breakup of confined gas threads in a cross-flowing liquid.
- To analyze the role of internal liquid flow in the pinch-off process.
- To develop accurate predictions for the timing of bubble pinch-off.
Main Methods:
- Experimental observation of gas thread breakup in a microchannel.
- Analysis of liquid flow dynamics within the gas thread.
- Comparison of experimental results with theoretical models.
Main Results:
- Gas thread breakup at low capillary numbers (Ca < 10{-2}) is initiated by internal liquid flow, not Plateau-Rayleigh instability.
- This internal flow, driven by differential curvatures at the thread tip and neck, is faster than previously assumed.
- Accurate predictions of pinch-off time are achieved by understanding curvature evolution.
Conclusions:
- The dominant mechanism for confined gas thread breakup is internal liquid flow.
- Curvature-driven flow dynamics dictate the pinch-off process and timing.
- This research provides a more accurate model for bubble formation in microfluidic systems.
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