Is vorticity-banding due to an elastic instability?

Kang, Kyongok; Lettinga, M. P.; Dhont, Jan K. G.

doi:10.1007/s00397-007-0238-z

Cited by 19 publications

(8 citation statements)

References 40 publications

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“…Self-oscillations in deformation of multi-component soft matters under fixed deformation rates have been repeatedly described. [40][41][42][67][68][69] Analysis of experimental data and theoretical approaches show that this phenomenon is likely related with the co-existence of different structural forms of a multi-component material owing its creation by deformations. 43 Indeed, for a long time, it was supposed that self-oscillations in flow of complex liquids are connected with double-valued flow curves (''viscosity bifurcation'' as in ref.…”

Section: Rheological Properties Of Suspensionmentioning

confidence: 99%

“…39 Besides, periodic oscillations of bands with regular temporal-spatial variations of velocity at a fixed shear stress have been described. [40][41][42] Meanwhile, it is necessary to stress that the appearance of the two-zone flow (''shear banding'') in these cases is not related to the yielding and can be caused by different reasons, in particular the multibranch flow curves of some of these substances.…”

Section: Introductionmentioning

confidence: 99%

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Viscoplasticity and stratified flow of colloid suspensions

et al. 2012

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Investigation of the rheology of concentrated colloid suspensions and direct observation of their flow allowed us to find several effects inherent to these media as typical soft matter. So, at low stress amplitudes, these colloids behave as mild gels with frequency independent elastic modulus and low mechanical losses. Meanwhile, suspensions demonstrate dualism of properties: at a given shear rate, they behave as viscoplastic media with clearly expressed yielding, while at a given low stress the pronounced Newtonian plateau is detected. The increase in shear rates and stresses leads to the sharp drop of the apparent viscosity, which usually is treated as the yielding effect. Transition through the yield stress is of a dynamic nature because the threshold stress depends on time and suspensions are thixotropic yielding materials. In the transient shear rate range, an unstable regime of deformation appears. It manifests itself either as deformation thickening up to jamming, or as the excitation of selfoscillations. The measuring of rheological properties in varying volume-to-surface ratio of a sample proves that flow of a suspension with high velocity at constant shear stress actually proceeds in a narrow layer inside the instrument gap. This conclusion has been confirmed by direct visual observations demonstrating that a flux is separated into three layers. A wide almost motionless layer is seen near a stationary surface. Near a moving surface, a narrow band with linear velocity profile is detected. Between them, a rather wide transient layer is observed and shear rate in this layer exceeds the average (global) shear rate by several times. Approximately, only a half of the total volume of a suspension is involved in flow. So, we observed a three-band flux of a suspension not described before. Shearing leads to an anisotropic structure of a solid phase.

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Section: Rheological Properties Of Suspensionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Viscoplasticity and stratified flow of colloid suspensions

et al. 2012

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“…According to Hu et al, Region I is Newtonian, followed by a shear‐thickening region at which a reentrant zone is detected under stress‐controlled conditions, where nucleation occurs nonhomogeneously (Region II); Region III is shear thickening without a reentrant zone, where shear‐induced structures (SIS) nucleation occurs homogeneously; and a shear‐thinning behavior appears in Region IV. More recent articles have documented the occurrence of instabilities in Regions II and III and the formation of alternated bands in the vorticity direction only in Couette flow; these vorticity rings are not observed in other geometries …”

Section: Introductionmentioning

confidence: 99%

Predictions of flow instabilities in the shear‐thickening regime with an improved bautista–manero–puig model

et al. 2018

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The trajectories of chaotic fluctuations in dilute micellar solutions, which typically occur during the creation and destruction of shear‐induced structures in the flow inception of a 0.4 wt % cetyltrimethylammonium tosilate aqueous solution and an aqueous solution of 3 mM cetyyltrimethylammonium bromide‐sodium salicylate, are predicted here with an improved Bautista–Manero–Puig model. To determine the constancy of the model parameters with time, we applied successfully an integro‐differential approach. This methodology revealed that all the model parameters, but the elastic modulus is constant. The nature of the predicted fluctuations was analyzed by employing the exponent of Lyapunov. This analysis demonstrates that the fluctuations are chaotic deterministic in Regimes I and IV, whereas they are random in Region II. We found that the predictions of the modified model follow the experimental data and reveal that these fluctuations are related to the creation of elastic structures at the inception of shear flow. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3735–3745, 2018

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“…wormlike micelles, this multivalued property is in fact a universal indicator of a shear-banding instability, specifically, gradient banding, where the (formerly homogeneous) system separates in gradient direction into coexisting bands characterized by a smaller and a larger local shear rate 12 (note that this is different from the more exotic vorticity banding, i.e., the formation of bands along the vorticity direction as discussed e.g., in Refs. 11,12,28 ). In soft (colloidal) glasses, multi-valued functions σ ( γ) occur as transient phenomena after a sudden switch-on of shear stress (Bauschinger effect) 29 , or in the vicinity of the so-called yield stress 30 ; in these systems one observes strong dynamical heterogeneities 17 .…”

Section: Introductionmentioning

confidence: 99%

Manipulating shear-induced non-equilibrium transitions in colloidal films by feedback control

2015

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Using Brownian Dynamics (BD) simulations we investigate non-equilibrium transitions of sheared colloidal films under controlled shear stress σxz. In our approach the shear rate [small gamma, Greek, dot above] is a dynamical variable, which relaxes on a time scale τc such that the instantaneous, configuration-dependent stress σxz(t) approaches a pre-imposed value. Investigating the dynamics under this "feedback-control" scheme we find unique behavior in regions where the flow curve σxz([small gamma, Greek, dot above]) of the uncontrolled system is monotonic. However, in non-monotonic regions our method allows to select between dynamical states characterized by different in-plane structure and viscosities. Indeed, the final state strongly depends on τc relative to an intrinsic relaxation time of the uncontrolled system. The critical values of τc are estimated on the basis of a simple model.

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Is vorticity-banding due to an elastic instability?

Cited by 19 publications

References 40 publications

Viscoplasticity and stratified flow of colloid suspensions

Viscoplasticity and stratified flow of colloid suspensions

Predictions of flow instabilities in the shear‐thickening regime with an improved bautista–manero–puig model

Manipulating shear-induced non-equilibrium transitions in colloidal films by feedback control

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