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Interfacially driven instability in the microchannel flow of a shear-banding fluid
P Nghe1, S M Fielding, P Tabeling
1Laboratoire Microfluidique, MEMS et Nanostructures, UMR Gulliver CNRS-ESPCI 7083, France.
Physical Review Letters
|September 28, 2010
Summary
Researchers observed an instability at the interface of shear bands in wormlike micellar surfactant solutions. This instability, linked to velocity changes, matches theoretical predictions driven by normal stress differences.
Area of Science:
- Rheology
- Fluid Dynamics
- Soft Matter Physics
Background:
- Shear-banding flow is a complex phenomenon observed in various complex fluids, including wormlike micellar solutions.
- Understanding the dynamics at the interface between shear bands is crucial for predicting fluid behavior under flow.
- Previous theoretical models predicted instabilities at this interface, but experimental validation has been lacking.
Purpose of the Study:
- To experimentally resolve the spatial structure of shear-banding flow in a wormlike micellar surfactant solution.
- To investigate the dynamics and stability of the interface between shear bands.
- To compare experimental observations with theoretical predictions from the diffusive Johnson-Segalman model.
Main Methods:
- Microparticle image velocimetry (micro-PIV) was employed to measure velocity fields with high spatial resolution.
- Experiments were conducted using a straight microchannel geometry.
- Results were quantitatively compared with theoretical simulations of the diffusive Johnson-Segalman model.
Main Results:
- The spatial structure of shear-banding flow was successfully resolved.
- An instability was observed at the interface between shear bands, characterized by velocity modulations along the vorticity direction.
- Quantitative agreement was found between experimental data and the theoretical model.
Conclusions:
- The experimental observation of an interface instability provides validation for theoretical predictions.
- The instability is driven by a normal stress jump across the interface between shear bands.
- This finding advances the understanding of complex fluid rheology and shear-banding phenomena.
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