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MICROFLUDIC APPLICATIONS OF BUBBLE OSCILLATIONS INDUCED BY GEOMETRICAL CONSTRAINT

Ongodiebi, Zuonaki

[Thesis]. Manchester, UK: The University of Manchester; 2014.

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Abstract

We present an experimental study of the propagation of air finger/bubble through a fluid-filled microchannel with centered rectangular occlusion. The displacement of a wetting fluid (oil) by a non-wetting fluid (air) at a constant flow rate results in a family of steadily propagating fingers/bubbles analogous to the propagation modes recently reported by [15, 16, 17] in millimetre-scale tubes, indicating that gravity is not an essential physical mechanism that underpins the emergence of these states. The occurance of these propagation modes informed by a simple modification of the tube geometry revealed that models based on idealized pore geometries are not able to capture key features of a complex practical flows. As the capillary number increases beyond a critical capillary number, the bubbles either localized in the least-constricted regions of the cross section or exhibit spatial oscillations formed by periodic sideways motion of the interface at a fixed distance behind the moving finger tip. We found that the transition from symmetric to either localized or oscillatory state results fom exchange of stability between two different states rather than a continous evolution from one state to another. Also, our experimental evidence suggests that the propagating fingers are dependent on the dimension of the channel and the obstacle. Our results reveal that air fingers and finite bubbles of aspect ratios greater than one exhibit propagation modes that are both quantitatively and qualitatively similar; but short bubbles with aspect ratios less than one undergo a transition similar to that of a continous transition from one state to another. Our results conform with recent report of [34].

Bibliographic metadata

Type of resource:
Content type:
Form of thesis:
Type of submission:
Degree type:
Master of Philosophy
Degree programme:
MPhil Mathematical Sciences
Publication date:
Location:
Manchester, UK
Total pages:
54
Abstract:
We present an experimental study of the propagation of air finger/bubble through a fluid-filled microchannel with centered rectangular occlusion. The displacement of a wetting fluid (oil) by a non-wetting fluid (air) at a constant flow rate results in a family of steadily propagating fingers/bubbles analogous to the propagation modes recently reported by [15, 16, 17] in millimetre-scale tubes, indicating that gravity is not an essential physical mechanism that underpins the emergence of these states. The occurance of these propagation modes informed by a simple modification of the tube geometry revealed that models based on idealized pore geometries are not able to capture key features of a complex practical flows. As the capillary number increases beyond a critical capillary number, the bubbles either localized in the least-constricted regions of the cross section or exhibit spatial oscillations formed by periodic sideways motion of the interface at a fixed distance behind the moving finger tip. We found that the transition from symmetric to either localized or oscillatory state results fom exchange of stability between two different states rather than a continous evolution from one state to another. Also, our experimental evidence suggests that the propagating fingers are dependent on the dimension of the channel and the obstacle. Our results reveal that air fingers and finite bubbles of aspect ratios greater than one exhibit propagation modes that are both quantitatively and qualitatively similar; but short bubbles with aspect ratios less than one undergo a transition similar to that of a continous transition from one state to another. Our results conform with recent report of [34].
Thesis main supervisor(s):
Thesis co-supervisor(s):
Language:
en

Institutional metadata

University researcher(s):

Record metadata

Manchester eScholar ID:
uk-ac-man-scw:243527
Created by:
Ongodiebi, Zuonaki
Created:
15th December, 2014, 15:54:06
Last modified by:
Ongodiebi, Zuonaki
Last modified:
1st December, 2017, 09:07:32

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