### 2019

Guillaume Duclos; Raymond Adkins; Debarghya Banerjee; Matthew S E Peterson; Minu Varghese; Itamar Kolvin; Arvind Baskaran; Robert A Pelcovits; Thomas R Powers; Aparna Baskaran; Federico Toschi; Michael F Hagan; Sebastian J Streichan; Vincenzo Vitelli; Daniel A Beller; Zvonimir Dogic

Topological structure and dynamics of three dimensional active nematics Journal Article

In: arXiv, 2019, (13 pages, 5 figures, plus Supplementary Information of 12 pages, 4 figures).

Abstract | BibTeX | Tags: cond-mat.soft

@article{e86486974c294689ad18cb25f012fe2e,

title = {Topological structure and dynamics of three dimensional active nematics},

author = {Guillaume Duclos and Raymond Adkins and Debarghya Banerjee and {Matthew S E } Peterson and Minu Varghese and Itamar Kolvin and Arvind Baskaran and {Robert A } Pelcovits and {Thomas R } Powers and Aparna Baskaran and Federico Toschi and {Michael F } Hagan and {Sebastian J } Streichan and Vincenzo Vitelli and {Daniel A } Beller and Zvonimir Dogic},

year = {2019},

date = {2019-01-01},

journal = {arXiv},

publisher = {Cornell University Library},

abstract = {Point-like motile topological defects control the universal dynamics of diverse two-dimensional active nematics ranging from shaken granular rods to cellular monolayers. A comparable understanding in higher dimensions has yet to emerge. We report the creation of three-dimensional active nematics by dispersing extensile microtubule bundles in a passive colloidal liquid crystal. Light-sheet microscopy reveals the millimeter-scale structure of active nematics with a single bundle resolution and the temporal evolution of the associated nematic director field. The dominant excitations of three-dimensional active nematics are extended charge-neutral disclination loops that undergo complex dynamics and recombination events. These studies introduce a new class of non-equilibrium systems whose turbulent-like dynamics arises from the interplay between internally generated active stresses, the chaotic flows and the topological structure of the constituent defects.},

note = {13 pages, 5 figures, plus Supplementary Information of 12 pages, 4 figures},

keywords = {cond-mat.soft},

pubstate = {published},

tppubtype = {article}

}

Xiao Xue; Luca Biferale; Mauro Sbragaglia; Federico Toschi

Particle settling in a fluctuating multicomponent fluid under confinement Journal Article

In: arXiv, 2019, (12pages, 7 figures).

Abstract | BibTeX | Tags: cond-mat.soft, physics.comp-ph, physics.flu-dyn

@article{d03238a0027f4132ad45a1d7327e35d7,

title = {Particle settling in a fluctuating multicomponent fluid under confinement},

author = {Xiao Xue and Luca Biferale and Mauro Sbragaglia and Federico Toschi},

year = {2019},

date = {2019-01-01},

journal = {arXiv},

publisher = {Cornell University Library},

abstract = {We study the motion of a spherical particle driven by a constant volume force in a confined channel with a fixed square cross-section. The channel is filled with a mixture of two liquids under the effect of thermal fluctuations. We use the lattice Boltzmann method to simulate a fluctuating multicomponent fluid in the mixed-phase, and particle-fluid interactions are tuned to reproduce different wetting properties at the particle surface. The numerical set-up is first validated in the absence of thermal fluctuations; to this aim, we quantitatively compute the drift velocity at changing the particle radius and compare it with previous experimental and numerical data. In the presence of thermal fluctuations, we study the fluctuations in the particle's velocity at changing thermal energy, applied force, particle size, and particle wettability. The importance of fluctuations with respect to the mean drift velocity is quantitatively assessed, especially in comparison to unconfined situations. Results show that confinement strongly enhances the importance of velocity fluctuations, which can be one order of magnitude larger than what expected in unconfined domains. The observed findings underscore the versatility of the lattice Boltzmann simulations in concrete applications involving the motion of colloidal particles in a highly confined environment in the presence of thermal fluctuations.},

note = {12pages, 7 figures},

keywords = {cond-mat.soft, physics.comp-ph, physics.flu-dyn},

pubstate = {published},

tppubtype = {article}

}

Roberto Benzi; Thibaut Divoux; Catherine Barentin; S é; Mauro Sbragaglia; Federico Toschi

Unified theoretical and experimental view on transient shear banding Journal Article

In: arXiv, 2019, (5 pages, 4 figures - supplemental 5 pages, 4 figures).

Abstract | BibTeX | Tags: cond-mat.soft, cond-mat.stat-mech, physics.flu-dyn

@article{67228bed5d894c6688f967ac3899f499,

title = {Unified theoretical and experimental view on transient shear banding},

author = {Roberto Benzi and Thibaut Divoux and Catherine Barentin and S é and Mauro Sbragaglia and Federico Toschi},

year = {2019},

date = {2019-01-01},

journal = {arXiv},

publisher = {Cornell University Library},

abstract = {Dense emulsions, colloidal gels, microgels, and foams all display a solid-like behavior at rest characterized by a yield stress, above which the material flows like a liquid. Such a fluidization transition often consists of long-lasting transient flows that involve shear-banded velocity profiles. The characteristic time for full fluidization, $tau_textf$, has been reported to decay as a power-law of the shear rate $dot gamma$ and of the shear stress $sigma$ with respective exponents $alpha$ and $beta$. Strikingly, the ratio of these exponents was empirically observed to coincide with the exponent of the Herschel-Bulkley law that describes the steady-state flow behavior of these complex fluids. Here we introduce a continuum model based on the minimization of an out-of-equilibrium free energy that captures quantitatively all the salient features associated with such textittransient shear-banding. More generally, our results provide a unified theoretical framework for describing the yielding transition and the steady-state flow properties of yield stress fluids.},

note = {5 pages, 4 figures - supplemental 5 pages, 4 figures},

keywords = {cond-mat.soft, cond-mat.stat-mech, physics.flu-dyn},

pubstate = {published},

tppubtype = {article}

}