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Folding of viscous threads in diverging microchannels
Thomas Cubaud1, Thomas G Mason
1Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, California 90095, USA.
Physical Review Letters
|April 12, 2006
Summary
A viscous thread in a microchannel bends to minimize energy loss, with folding influenced by flow rates. This microfluidic system controls thread bending and enhances mixing of dissimilar liquids.
Area of Science:
- Fluid dynamics
- Microfluidics
- Rheology
Background:
- Viscous thread behavior in microchannels is crucial for controlling fluid interfaces.
- Diverging microchannels induce complex flow patterns affecting thread dynamics.
- Minimizing viscous dissipation is a key principle governing fluid instabilities.
Purpose of the Study:
- Investigate the folding instability of a viscous thread in a diverging microchannel.
- Understand how flow rates and channel geometry influence thread morphology.
- Explore the role of diffusive mixing on folding flow patterns and mixing enhancement.
Main Methods:
- Utilized microfluidic experiments with a viscous thread in a miscible liquid.
- Analyzed thread folding dynamics in response to a square to diverging channel transition.
- Quantified folding frequency and thread diameter in relation to flow rates and shear rates.
Main Results:
- The viscous thread exhibits folding instability, forming bends to minimize viscous dissipation.
- Folding frequency and thread diameter correlate with volume flow rates and characteristic shear rate.
- Diffusive mixing significantly alters folding flow morphologies and enhances inter-liquid mixing.
Conclusions:
- Microfluidic systems can control viscous thread bending and enhance mixing.
- The folding instability is a mechanism for managing viscous dissipation in diverging flows.
- This study provides insights into controlling interfacial dynamics for applications in microfluidic mixing.
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