Rheology of active emulsions with negative effective viscosity

Favuzzi, Ilario; Carenza, Livio Nicola; Corberi, Federico; Gonnella, Giuseppe; Lamura, A.; Negro, Giuseppe

doi:10.1080/1539445x.2021.1908357

Cited by 7 publications

(5 citation statements)

References 49 publications

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“…A few other articles deal with hydrodynamic-interactions and their impact on rheology in semi-dilute regime, see [45,43,55]. More complicated settings were also recently studied, like micro-swimmers in nematic liquid crystals [5], viscoelastic fluids [38] or in emulsions [16].…”

Section: Introductionmentioning

confidence: 99%

Derivation of an effective rheology for dilute suspensions of micro-swimmers

Girodroux-Lavigne¹

2022

Preprint

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We provide a rigorous derivation of an effective rheology for dilute viscous suspensions of self-propelled particles. We derive at the limit an effective Stokes system with two additional terms. The first term corresponds to an effective viscosity that matches the famous Einstein's formula µ ef f = (1 + 5 2 λ)µ. The second additional term derived is an effective active stress σ 1 that appears as a forcing term λ div σ 1 in the fluid equation. We then investigate the effects of this term depending on the micro-swimmers nature and their distribution in the fluid.

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Section: Introductionmentioning

confidence: 99%

Derivation of an effective rheology for dilute suspensions of micro-swimmers

Girodroux-Lavigne¹

2022

Preprint

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“…We hope that our results will stimulate experiments, e.g., with stabilized oil-in-water or water-in-oil emulsions, to directly test our predictions on the scaling of f c and on the importance of permeation for the yielding transition. To assess the universality of our results, one could investigate the yielding transition in other materials, such as biological tissues (33,49,50), red blood cell suspensions (51), and liquid crystalline emulsions (52)(53)(54)(55). It would also be of interest to revisit the foam limit considered in previous literature (7,8) to quantify permeation there and to ask whether the nonconserved and conserved model are fundamentally distinct in that limit as well.…”

Section: Discussionmentioning

confidence: 99%

Yield-stress transition in suspensions of deformable droplets

et al. 2023

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Yield-stress materials, which require a sufficiently large forcing to flow, are currently ill-understood theoretically. To gain insight into their yielding transition, we study numerically the rheology of a suspension of deformable droplets in 2D. We show that the suspension displays yield-stress behavior, with droplets remaining motionless below a critical body-force. In this phase, droplets jam to form an amorphous structure, whereas they order in the flowing phase. Yielding is linked to a percolation transition in the contacts of droplet-droplet overlaps and requires strict conservation of the droplet area to exist. Close to the transition, we find strong oscillations in the droplet motion that resemble those found experimentally in confined colloidal glasses. We show that even when droplets are static, the underlying solvent moves by permeation so that the viscosity of the composite system is never truly infinite, and its value ceases to be a bulk material property of the system.

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“…For simplicity, we used the D2Q9 lattice model on a uniform square 2D lattice to analyze the multicomponent flow when ∆x = ∆t = 1 [40,41]. This model has nine velocities and is widely applied in 2D simulations [42,43]. Although the D2Q9 lattice model with eighth-order isotropy could not reduce the spurious current enough [44], when the droplet moves quickly in microchannels, the spurious currents may have a limit influence on the droplet dynamics.…”

Section: Numerical Methods 21 Pseudopotential Lattice Boltzmann Model...mentioning

confidence: 99%

Pseudopotential Lattice Boltzmann Model for Immiscible Multicomponent Flows in Microchannels

Liu

2023

Processes

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To investigate droplet formation in a microchannel with different walls, simulations were conducted based on a pseudopotential model using the exact difference method force scheme. The variable surface tension was obtained using Laplace’s law, and the static contact angle was estimated using a first-order linear equation of the corresponding control parameter of the model. The droplet motion in microchannels was simulated using our model, and the effects of surface wettability and the Bond number on the droplet motion were investigated. The droplet motion for the intermediate microchannel wall took a significantly shorter time than that for the hydrophilic wall, and the wet length also depended on the contact angle. As the Bond number increased, the wet length of the droplet decreased on the hydrophilic surface. The droplet formation in a T-junction device was also simulated using the proposed model, and the effects of the capillary number and viscosity ratio on droplet formation were discussed in detail, and some empirical correlations between the capillary number and dimensionless droplet length are presented according to different viscosity ratios. The three flow patterns of droplet formation were categorized by the different capillary numbers as the dripping–squeezing, jetting–shearing, and threading regimes. In the dripping–squeezing regime, the droplet volume was nearly independent of the viscosity ratio, but the viscous effect was more prone to occur in the jetting–shearing regime. In the jetting–shearing regime, as the capillary number increased, the effect of the viscosity ratio on droplet formation became more significant.

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Rheology of active emulsions with negative effective viscosity

Cited by 7 publications

References 49 publications

Derivation of an effective rheology for dilute suspensions of micro-swimmers

Derivation of an effective rheology for dilute suspensions of micro-swimmers

Yield-stress transition in suspensions of deformable droplets

Pseudopotential Lattice Boltzmann Model for Immiscible Multicomponent Flows in Microchannels

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