Rheology and dynamics of dense particle suspensions in rotary shear flows
Agrawal, Naveen Kumar ; Ge, Zhouyang ; Trulsson, Martin LU
; Tammisola, Outi
and Brandt, Luca
(2025)
In Journal of Fluid Mechanics
1018.
- Abstract
We introduce a novel unsteady shear protocol, which we name rotary shear (RS), where the flow and vorticity directions are continuously rotated around the velocity-gradient direction by imposing two out-of-phase oscillatory shears (OSs) in orthogonal directions. We perform numerical simulations of dense suspensions of rigid non-Brownian spherical particles at volume fractions between 0.40 and 0.55, subject to this new RS protocol, and compare with the classical OS protocol. We find that the suspension viscosity displays a similar non-monotonic response as the strain amplitude is increased: a minimum viscosity is found at an intermediate, volume-fraction-dependent strain amplitude. However, the suspension dynamics is different in the new... (More)
We introduce a novel unsteady shear protocol, which we name rotary shear (RS), where the flow and vorticity directions are continuously rotated around the velocity-gradient direction by imposing two out-of-phase oscillatory shears (OSs) in orthogonal directions. We perform numerical simulations of dense suspensions of rigid non-Brownian spherical particles at volume fractions between 0.40 and 0.55, subject to this new RS protocol, and compare with the classical OS protocol. We find that the suspension viscosity displays a similar non-monotonic response as the strain amplitude is increased: a minimum viscosity is found at an intermediate, volume-fraction-dependent strain amplitude. However, the suspension dynamics is different in the new protocol. Unlike the OS protocol, suspensions under RS do not show absorbing states at any and do not undergo the reversible-irreversible transition: the stroboscopic particle dynamics is always diffusive, which we attribute to the fact that the RS protocol is inherently irreversible due to its design. To validate this hypothesis, we introduce a reversible-RS (RRS) protocol, a combination of RS and OS, where we rotate the shear direction (as in RS) until it is instantaneously reversed (as in OS), and find the resulting rheology and dynamics to be closer to OS. Detailed microstructure analysis shows that both the OS and RRS protocols result in a contact-free, isotropic to an in-contact, anisotropic microstructure at the dynamically reversible-to-irreversible transition. The RS protocol does not render such a transition, and the dynamics remains diffusive with an in-contact, anisotropic microstructure for all strain amplitudes.
(Less)
- author
- Agrawal, Naveen Kumar
; Ge, Zhouyang
; Trulsson, Martin
LU
; Tammisola, Outi
and Brandt, Luca
- organization
- publishing date
- 2025-09
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- particle/fluid flow, rheology, suspensions
- in
- Journal of Fluid Mechanics
- volume
- 1018
- article number
- A51
- publisher
- Cambridge University Press
- external identifiers
-
- scopus:105015399138
- ISSN
- 0022-1120
- DOI
- 10.1017/jfm.2025.10535
- language
- English
- LU publication?
- yes
- id
- 9b035500-05f8-4b9a-8331-fa1155db18d6
- date added to LUP
- 2025-10-15 11:58:08
- date last changed
- 2025-10-15 11:58:38
@article{9b035500-05f8-4b9a-8331-fa1155db18d6,
abstract = {{<p>We introduce a novel unsteady shear protocol, which we name rotary shear (RS), where the flow and vorticity directions are continuously rotated around the velocity-gradient direction by imposing two out-of-phase oscillatory shears (OSs) in orthogonal directions. We perform numerical simulations of dense suspensions of rigid non-Brownian spherical particles at volume fractions between 0.40 and 0.55, subject to this new RS protocol, and compare with the classical OS protocol. We find that the suspension viscosity displays a similar non-monotonic response as the strain amplitude is increased: a minimum viscosity is found at an intermediate, volume-fraction-dependent strain amplitude. However, the suspension dynamics is different in the new protocol. Unlike the OS protocol, suspensions under RS do not show absorbing states at any and do not undergo the reversible-irreversible transition: the stroboscopic particle dynamics is always diffusive, which we attribute to the fact that the RS protocol is inherently irreversible due to its design. To validate this hypothesis, we introduce a reversible-RS (RRS) protocol, a combination of RS and OS, where we rotate the shear direction (as in RS) until it is instantaneously reversed (as in OS), and find the resulting rheology and dynamics to be closer to OS. Detailed microstructure analysis shows that both the OS and RRS protocols result in a contact-free, isotropic to an in-contact, anisotropic microstructure at the dynamically reversible-to-irreversible transition. The RS protocol does not render such a transition, and the dynamics remains diffusive with an in-contact, anisotropic microstructure for all strain amplitudes.</p>}},
author = {{Agrawal, Naveen Kumar and Ge, Zhouyang and Trulsson, Martin and Tammisola, Outi and Brandt, Luca}},
issn = {{0022-1120}},
keywords = {{particle/fluid flow; rheology; suspensions}},
language = {{eng}},
publisher = {{Cambridge University Press}},
series = {{Journal of Fluid Mechanics}},
title = {{Rheology and dynamics of dense particle suspensions in rotary shear flows}},
url = {{http://dx.doi.org/10.1017/jfm.2025.10535}},
doi = {{10.1017/jfm.2025.10535}},
volume = {{1018}},
year = {{2025}},
}