High shear rheology of shear banding fluids in microchannels

2008 ◽  
Vol 93 (20) ◽  
pp. 204102 ◽  
Author(s):  
Philippe Nghe ◽  
Guillaume Degré ◽  
Patrick Tabeling ◽  
Armand Ajdari
Keyword(s):  
Shear Banding ◽  
High Shear ◽  
Shear Rheology ◽  
High Shear Rheology

High Shear Rheology and Anisotropy in Concentrated Solutions of Monoclonal Antibodies

2013 ◽  
Vol 102 (8) ◽  
pp. 2538-2549 ◽  
Author(s):  
Isidro E. Zarraga ◽  
Rosalynn Taing ◽  
Jonathan Zarzar ◽  
Jacob Luoma ◽  
Jenny Hsiung ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
High Shear ◽  
Concentrated Solutions ◽  
Shear Rheology ◽  
High Shear Rheology

Rheology of Nanofluids in Microchannels

2008 ◽  
Author(s):  
Fre´de´ric Ayela ◽  
Olivier Tillement ◽  
Julien Chevalier
Keyword(s):  
Rheological Properties ◽  
Peclet Number ◽  
High Shear ◽  
Shear Rheology ◽  
Péclet Number ◽  
Shear Rates ◽  
High Shear Rates ◽  
On Chip ◽  
Very High ◽  
High Shear Rheology

Microfluidics is often presented for applications where only microliters sample volumes are available. But the benefits of microchannels do not reduce to a low consumption of fluids. From a physical and mechanical point of view, microfluidics can offer high shear rates combined with low Reynolds number and low viscous heating. It becomes possible to explore high shear rheology on a lab-on-chip. We have micromachined microviscometers to study the rheological properties of nanofluids under very high shear rates conditions. Nanofluids are fluid suspensions of solid nanoparticles. Recent experiments have indicated an anomalous increase in thermal conductivity of these suspensions. But less attention has been payed to the rheological properties of nanofluids. The few results concerning the viscosity of nanofluids exhibit scattered values higher than those of fluid suspensions of microparticles, because of a higher rate of collisions due to Brownian motion and shearing motion which enhance aggregation. These experiments were performed with commercially available rheometers over a limited range of shear rates. Our viscometers on chip are silicon — Pyrex microchannels (H ≈ 10 – 20 μm) equipped with local pressure drop sensors. Nanofluids under test were ethanol-based SiO2 nanoparticles. For particle sizes from 20 nm to 190 nm, and solid volume fractions from 1.4% to 7%, a newtonian behaviour has been observed up to 5.104 s−1. High shear rheology is the only way to reach high Peclet number values with nanoparticles in a laminar flow. It was possible to cover a wide range of Peclet number and to have Pe > 1 with diameter in the tens of nanometers range. Our results have demonstrated that an apparent solid volume fraction φa > φ, due to aggregation, was responsible of the increment of viscosity. More important was the demonstration that the shape of the clusters could be modified and that the ratio φa/φ could be lowered by a very high shear rate. Very high shearing rates in microchannels appear to be a way for nanofluids to converge to a well-defined value of viscosities.

The high shear rheology of lithographic emulsions

2000 ◽  
Vol 83 (5) ◽  
pp. 234-239 ◽  
Author(s):  
M. J. Thompson ◽  
M. R. Mackley ◽  
J. A. Nimmo
Keyword(s):  
High Shear ◽  
Shear Rheology ◽  
High Shear Rheology

scholarly journals Microgels as viscosity modifiers influence lubrication performance of continuum

Soft Matter ◽  
2019 ◽  
Vol 15 (47) ◽  
pp. 9614-9624 ◽  
Author(s):  
Efren Andablo-Reyes ◽  
Demetra Yerani ◽  
Ming Fu ◽  
Evangelos Liamas ◽  
Simon Connell ◽  
...  
Keyword(s):  
Tribological Performance ◽  
High Shear ◽  
Shear Rheology ◽  
Lubrication Performance ◽  
Viscosity Modifiers ◽  
High Shear Rheology ◽  
The Continuum

Biocompatible microgels modify the rheology of continuum acting as thickening or thinning agents. Here, the influence of high shear rheology of microgels on tribological performance of the continuum is demonstrated.

High shear rheology of paper coating colors - more than just viscosity

1997 ◽  
Vol 20 (8) ◽  
pp. 557-563 ◽  
Author(s):  
Norbert Willenbacher ◽  
Haryutum Hanciogullari ◽  
Hans G. Wagner
Keyword(s):  
High Shear ◽  
Paper Coating ◽  
Shear Rheology ◽  
High Shear Rheology

scholarly journals RARE Velocimetry of Shear Banded Flow in Cylindrical Couette Geometry

2021 ◽  
Author(s):  
◽  
Stefan Kuczera
Keyword(s):  
Shear Rate ◽  
High Resolution ◽  
Complex Fluids ◽  
Shear Banding ◽  
Velocity Profiles ◽  
High Shear Rate ◽  
Flow Instabilities ◽  
High Shear ◽  
Shear Rates ◽  
Temporal And Spatial

<p>A flow phenomena called ‘shear banding’ is often observed for a certain class of complex fluids, namely wormlike micellar solutions. Wormlike micelles are elongated flexible self-assembly structures formed by the aggregation of amphiphiles, which may entangle into a dynamic network above a certain concentration threshold. The entanglement results in the sample having both solid-like (elastic) and liquid-like (viscous) properties, an ambiguity commonly found in complex fluids. Under certain shear conditions, the flow couples with the structure of the micellar network, leading to the formation of (shear) bands with differing viscosity.  The principle goal of this work is to address open questions regarding the temporal and spatial stability of shear banded flow. Shear banding is often studied in cylindrical Couette cells, where the fluid is sheared in a gap between differentially rotating concentric cylinders. For the sake of an accurate description of the flow in such a shear cell, the methodology for a 2D Nuclear Magnetic Resonance (NMR) velocimetry technique (known as PGSE-RARE), which offers high temporal and spatial resolution, is improved and refined. Two main challenges are identified and overcome. The first concerns the fact that the velocity imaging process operates on a Cartesian grid, whereas the flow in the Couette cell is of cylindrical symmetry. Numerical calculations and NMR simulations based on the Bloch equations, as well as experimental evidence, give insight on the appropriate selection of the fluid volume over which velocity information is accumulated and the preferred scheme through which the NMR image is acquired in the so-called k-space. The small extent of the fluid gap for the cells in use is the second challenge. In this respect, a variant of the velocimetry technique is developed, which offers ultra high resolution in the gap direction, necessary for a detailed description of the flow profile in the banded state.  The refined methodology is applied in a thorough study of a certain wormlike micellar solution (‘10% CPCl’), which is known to exhibit spatiotemporal fluctuations and has been subject of numerous studies over the past 20 years. NMR results are supported by a recently developed 2D Rheo-USV (Ultrasonic Speckle Velocimetry) method, which offers an even higher temporal resolution. The two complementary methods show good agreement for averaged velocity profiles. In line with previous studies the fluid is found to follow a standard anomalous lever rule, which is characterized by a constant shear rate in the high viscosity band and a varying shear rate and proportion of the high shear rate band. In particular, the high resolution NMR variant allows a refined picture on the dynamics of the interface between the two bands. Furthermore, slip is observed for all investigated shear rates. The amount of slip, however, is found to strongly depend on the specifities of the Couette cells in use. Spatially and temporally resolved flow maps reveal various flow instabilities. Ultrasound measurements show vorticity structures in the order of the gap width. In the NMR case no such structures are observed due to the lower resolution in the axial direction. For higher shear rates the occurrence of turbulent bursts is detected for USV. No direct evidence of similar flow instabilities is found in the NMR case. Finally, broad distributions dominate the high shear rate band in temporally and spatially resolved velocity profiles, showing the fluctuative nature of the flow.</p>

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