A rheo-optical study of shear rate and optical anisotropy in wormlike micelles solutions

Raudsepp, Allan; Callaghan, Paul T.

doi:10.1039/b713416a

Cited by 17 publications

(14 citation statements)

References 51 publications

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“…2.b)] (this last observation is robust as long as the shear-banding flow does not become turbulent, depending on the value of Λ). All these features are consistent with our previous investigation of the 10% CPCl/NaSal solution [39] and seem to be widespread across shear-banding micellar systems [19,[43][44][45].…”

Section: Observing Secondary Flowssupporting

confidence: 79%

Interplay between elastic instabilities and shear-banding: three categories of Taylor–Couette flows and beyond

et al. 2012

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In the past twenty years, shear-banding flows have been probed by various techniques, such as rheometry, velocimetry and flow birefringence. In micellar solutions, many of the data collected exhibit unexplained spatiotemporal fluctuations. Recently, it has been suggested that those fluctuations originate from a purely elastic instability of the shear-banding flow. In cylindrical Couette geometry, the instability is reminiscent of the Taylor-like instability observed in viscoelastic polymer solutions. The criterion for purely elastic Taylor-Couette instability adapted to shear-banding flows suggested three categories of shear-banding depending on their stability. In the present study, we report on a large set of experimental data which demonstrates the existence of the three categories of shear-banding flows in various surfactant solutions. Consistent with theoretical predictions, increases in the surfactant concentration or in the curvature of the geometry destabilize the flow, whereas an increase in temperature stabilizes the flow. But experiments also exhibit some interesting behaviors going beyond the purely elastic instability criterion.

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Section: Observing Secondary Flowssupporting

confidence: 79%

Interplay between elastic instabilities and shear-banding: three categories of Taylor–Couette flows and beyond

et al. 2012

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“…In this context, the question of the correspondence between shear and birefringence bands has been raised by some authors [169,170]. In recent studies of semi-dilute CPCl/NaSal solutions, simultaneous measurements of velocity profiles and optical visualisations were performed, showing a good agreement between shear and birefringence bands [157,253]. However, this correlation did not seem so obvious for other systems [169,170].…”

Section: Direct Observation Using Flow Birefringencementioning

confidence: 99%

Shear-Induced Transitions and Instabilities in Surfactant Wormlike Micelles

Lerouge

Berret

2009

Polymer Characterization

147

153

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In this review, we report recent developments on the shear-induced transitions and instabilities found in surfactant wormlike micelles. The survey focuses on the nonlinear shear rheology and covers a broad range of surfactant concentrations, from the dilute to the liquid-crystalline states and including the semidilute and concentrated regimes. Based on a systematic analysis of many surfactant systems, the present approach aims to identify the essential features of the transitions. It is suggested that these features define classes of behaviors. The review describes three types of transitions and/or instabilities: the shear-thickening found in the dilute regime, the shear-banding which is linked in some systems to the isotropic-tonematic transition, and the flow-aligning and tumbling instabilities characteristic of nematic structures. In these three classes of behaviors, the shear-induced transitions are the result of a coupling between the internal structure of the fluid and the flow, resulting in a new mesoscopic organization under shear. This survey finally highlights the potential use of wormlike micelles as model systems for complex fluids and for applications.

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“…In particular, the banded profile can depend on surface properties (Lettinga and Manneville 2009) and may not be constant along the vorticity direction (Lerouge et al 2008) in a cylindrical Couette cell. A commonly observed deviation from the simple lever rule is a varying local shear rate in the high shear rate portion of the fluid as one sweeps through the stress plateau (e.g., Raudsepp and Callaghan (2008) and Helgeson et al (2009)). Following recent literature (Fardin et al 2012a), we shall speak of a standard anomalous lever rule if this behavior is detected in conjunction with wall slip.…”

Section: Introductionmentioning

confidence: 98%

Anomalous shear banding revisited with Rheo-NMR and Rheo-USV

et al. 2015

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A combined two-dimensional Rheo-NMR velocimetry and two-dimensional Rheo-USV approach is used to further elucidate the flow of a wormlike micellar solution in cylindrical Couette geometries. Recent experimental enhancements for both methods enable a more detailed description of the flow dynamics than available in the past. This enabled us to revisit and investigate shear banded flow utilizing improved spatial and temporal resolution, clearly confirming a departure from a simple lever rule for the micellar solution under study. Both experimental techniques observe different shear rates in the high shear rate band accompanied by a varying position of the interface between bands for different applied shear rates. Furthermore, spatially and temporally resolved velocimetry reveals various flow instabilities. Ultrasound measurements show vorticity undulations with wavelengths that scale linearly with the size of the high shear rate band. For high enough shear rates, the occurrence of turbulent bursts is detected in the USV case. However, no direct evidence of these bursts is found in the NMRmeasurements for equivalent shear rates, which we attribute so far to differences in the design of the shearing geometries.

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A rheo-optical study of shear rate and optical anisotropy in wormlike micelles solutions

Cited by 17 publications

References 51 publications

Interplay between elastic instabilities and shear-banding: three categories of Taylor–Couette flows and beyond

Interplay between elastic instabilities and shear-banding: three categories of Taylor–Couette flows and beyond

Shear-Induced Transitions and Instabilities in Surfactant Wormlike Micelles

Anomalous shear banding revisited with Rheo-NMR and Rheo-USV

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