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Painting Taylor vortices with cellulose nanocrystals : Suspension flow supercritical spectral dynamics

Ghanbari, Reza LU ; Pashazadeh, Sajjad ; Sekar, Kesavan ; Nygård, Kim LU ; Terry, Ann LU ; Liebi, Marianne LU ; Matic, Aleksandar and Kádár, Roland LU (2024) In Physics of Fluids 36(4).
Abstract

We study the flow stability and spatiotemporal spectral dynamics of cellulose nanocrystal (CNC) suspensions in a custom Taylor-Couette flow cell using the intrinsic shear induced birefringence and liquid crystalline properties of CNC suspensions for flow visualizations, for the first time. The analysis is performed at constant ramped speed inputs of the independently rotating cylinders for several cases ranging from only inner or outer rotating cylinders to three counter-rotation cases. All CNC suspensions have measurable elasticity and shear thinning, both increasing with CNC concentration. We show that the flow patterns recorded are essentially Newtonian-like, with non-Newtonian effects ranging from a decrease in wavenumbers to... (More)

We study the flow stability and spatiotemporal spectral dynamics of cellulose nanocrystal (CNC) suspensions in a custom Taylor-Couette flow cell using the intrinsic shear induced birefringence and liquid crystalline properties of CNC suspensions for flow visualizations, for the first time. The analysis is performed at constant ramped speed inputs of the independently rotating cylinders for several cases ranging from only inner or outer rotating cylinders to three counter-rotation cases. All CNC suspensions have measurable elasticity and shear thinning, both increasing with CNC concentration. We show that the flow patterns recorded are essentially Newtonian-like, with non-Newtonian effects ranging from a decrease in wavenumbers to altering the critical parameters for the onset of instability modes. Outer cylinder rotation flow cases are stable for all concentrations whereas inner cylinder rotation flow cases transition to axisymmetric and azimuthally periodic secondary flows. However, counter-rotation cases become unstable to asymmetric spiral modes. With increasing CNC concentration, a counter-rotation case was found where azimuthally periodic wavy patterns transition to asymmetric spiral modes. Based on rheo-SAXS measurements, the shear-thinning region of CNC suspensions is expected to lead to the breakdown of the chiral nematic phase, whose elastic constants constitute the dominant structural elasticity mechanism. Thus, we interpret the Taylor-Couette stability of the CNC suspensions as dominated by their shear-thinning character due to the expected loss of elasticity in nonlinear flow conditions.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physics of Fluids
volume
36
issue
4
article number
044114
publisher
American Institute of Physics (AIP)
external identifiers
  • scopus:85190862799
ISSN
1070-6631
DOI
10.1063/5.0195130
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2024 Author(s).
id
5c0d9355-d2bd-4b8a-b3c7-8213cce95af5
date added to LUP
2025-01-14 14:48:58
date last changed
2025-04-04 14:47:53
@article{5c0d9355-d2bd-4b8a-b3c7-8213cce95af5,
  abstract     = {{<p>We study the flow stability and spatiotemporal spectral dynamics of cellulose nanocrystal (CNC) suspensions in a custom Taylor-Couette flow cell using the intrinsic shear induced birefringence and liquid crystalline properties of CNC suspensions for flow visualizations, for the first time. The analysis is performed at constant ramped speed inputs of the independently rotating cylinders for several cases ranging from only inner or outer rotating cylinders to three counter-rotation cases. All CNC suspensions have measurable elasticity and shear thinning, both increasing with CNC concentration. We show that the flow patterns recorded are essentially Newtonian-like, with non-Newtonian effects ranging from a decrease in wavenumbers to altering the critical parameters for the onset of instability modes. Outer cylinder rotation flow cases are stable for all concentrations whereas inner cylinder rotation flow cases transition to axisymmetric and azimuthally periodic secondary flows. However, counter-rotation cases become unstable to asymmetric spiral modes. With increasing CNC concentration, a counter-rotation case was found where azimuthally periodic wavy patterns transition to asymmetric spiral modes. Based on rheo-SAXS measurements, the shear-thinning region of CNC suspensions is expected to lead to the breakdown of the chiral nematic phase, whose elastic constants constitute the dominant structural elasticity mechanism. Thus, we interpret the Taylor-Couette stability of the CNC suspensions as dominated by their shear-thinning character due to the expected loss of elasticity in nonlinear flow conditions.</p>}},
  author       = {{Ghanbari, Reza and Pashazadeh, Sajjad and Sekar, Kesavan and Nygård, Kim and Terry, Ann and Liebi, Marianne and Matic, Aleksandar and Kádár, Roland}},
  issn         = {{1070-6631}},
  language     = {{eng}},
  number       = {{4}},
  publisher    = {{American Institute of Physics (AIP)}},
  series       = {{Physics of Fluids}},
  title        = {{Painting Taylor vortices with cellulose nanocrystals : Suspension flow supercritical spectral dynamics}},
  url          = {{http://dx.doi.org/10.1063/5.0195130}},
  doi          = {{10.1063/5.0195130}},
  volume       = {{36}},
  year         = {{2024}},
}