Start-up inertia as an origin for heterogeneous flow

Korhonen, Marko; Mohtaschemi, Mikael; Puisto, Antti; Illa, Xavier; Alava, Mikko J.

doi:10.1103/physreve.95.022608

Cited by 6 publications

(2 citation statements)

References 28 publications

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“…Despite the relative simplicity and generality of the model and the utilized geometry, we are able to show that large amplitude oscillatory shear induces considerable flow localization effects. These are the result of the inherent accelerating motion of the oscillating boundary condition in LAOS, which induces significant inertial effects equivalent to those in startup flows [23,24]. These then are capable of triggering structural heterogeneities when coupled to the fluid's nonlinear structural response to shear, leading to shear localization due to flow-concentration coupling, which has been reported for soft glasses [25][26][27] and hard spheres under LAOS [28].…”

Section: Introductionmentioning

confidence: 83%

Shear localization in large amplitude oscillatory shear (LAOS) flows of particulate suspensions

et al. 2021

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Strong shear localization effects are observed in large amplitude oscillatory shear (LAOS) simulations of a particulate suspension. Here, the structural response of this complex fluid is completely viscous and governed by the general shear-driven diffusion model by Phillips et al. [Phys. Fluids 4, 30 (1992)]. When coupled to oscillatory shear in LAOS, this model is shown to produce concentration gradients, which imply the existence of regions of disparate viscosities across the simulated measurement gap. This suggests the presence of strong shear localization which is conceived even though the intrinsic flow curve of the model is monotonic, and the simulated geometry is a planar Couette setup, expected to display simple shear flow characteristics. This shear localization is generated due to the oscillatory shear at the shearing plate, which, therefore, induces accelerating motion. The subsequent inertial effects act as perturbations in the nonlinear response of the fluid structure to shear and are sufficient to trigger significant localization in the flow. Due to the ubiquitous nature of shear-driven diffusive mechanisms in complex fluids, these results suggest shear localization to be an integral feature of a LAOS measurement of many complex fluids.

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Section: Introductionmentioning

confidence: 83%

Shear localization in large amplitude oscillatory shear (LAOS) flows of particulate suspensions

et al. 2021

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“…Finally, the Moorcroft-Fielding criteria have been established for planar Couette flow and the possible impact of the curvature inherent to the TC flow remains to be clarified. Possible effects of fluid inertia during flow startup should also be examined 65 .…”

Section: Discussionmentioning

confidence: 99%

Shear-banding fluid(s) under time-dependent shear flows. Part II: A test of the Moorcroft–Fielding criteria

Briole

Casanellas

Fardin

et al. 2021

Journal of Rheology

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Complex systems often exhibit shear banding -the coexistence of two different states characterized by their internal structuring and local shear rates. For some of them, the heterogeneous flow corresponds to the final steady state response while for others, shear banding can only be transient, the banding structure healing back to homogeneous flow in the ultimate steady state after long-lived periods. In order to explain the diversity of observations, Moorcroft and Fielding have established general criteria for the onset of banding in time-dependent flows of complex systems, ranging from polymeric fluids to soft glassy materials [Moorcroft et al., Phys. Rev. Lett., 2013, 110, 086001]. The proposed criteria are based on the time evolution of the bulk rheological response function of the system to a given time-dependent flow protocol and are associated with a specific signature in the mechanical response. In this contribution, we test the validity of these criteria in the case of two common time-dependent flow protocols: a step stress and a shear startup. Two types of fluids are examined. On the one hand, a wormlike micelles system exhibiting steady shear banding is studied experimentally, using rheometry coupled with direct visualisations and particle image velocimetry. On the other hand, we analyse previous literature on yield stress fluids exhibiting transient shear banding. Under creep flow, for both types of fluids the onset of banding arises in a time window compatible with the Moorcroft-Fielding criterion. However, the mechanical signature, i.e. the shape of the bulk mechanical signal as a function of time is not the one expected within some of the specific models with which the general Moorcroft-Fielding criteria were tested numerically. Under shear startup, both types of fluids behave differently. The criterion holds for yield stress fluids, the onset of banding arising just after the stress overshoot, as expected. On the contrary, for wormlike micelles the window of instability is delayed, even if the overshoot clearly plays a crucial role in the nucleation of the shear-induced structures. Regardless of the flow protocol or the system, wall slip seems to go hand in hand with banding indicating that it is a key ingredient to take into account.

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Dynamics and shear banding in stress-controlled start-up shear flow of a model aging soft materials: the role of inertia and thixotropy

2022

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Start-up inertia as an origin for heterogeneous flow

Cited by 6 publications

References 28 publications

Shear localization in large amplitude oscillatory shear (LAOS) flows of particulate suspensions

Shear localization in large amplitude oscillatory shear (LAOS) flows of particulate suspensions

Shear-banding fluid(s) under time-dependent shear flows. Part II: A test of the Moorcroft–Fielding criteria

Dynamics and shear banding in stress-controlled start-up shear flow of a model aging soft materials: the role of inertia and thixotropy

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