Large-scale simulation of steady and time-dependent active suspensions with the force-coupling method

Delmotte, Blaise; Keaveny, Eric E.; Plouraboué, Franck; Climent, Éric

doi:10.1016/j.jcp.2015.09.020

Cited by 43 publications

(68 citation statements)

References 77 publications

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“…In contrast, ABPs in 3D clearly exhibit MIPS [24][25][26] and large-scale collective motion [24]. Moreover, simulations of 2D, quasi-2D, and 3D systems of attractive squirmers show a substantially enhanced cluster formation compared to purely repulsive squirmers [35,36]. Also in such situations, hydrodynamics is found to reduce MIPS compared to ABPs.…”

Section: Collective Behavior Of Squirmers-brief Summary Of Previomentioning

confidence: 91%

Clustering of microswimmers: interplay of shape and hydrodynamics

et al. 2018

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The spatiotemporal dynamics in systems of active self-propelled particles is controlled by the propulsion mechanism in combination with various direct interactions, such as steric repulsion, hydrodynamics, and chemical fields. Yet, these direct interactions are typically anisotropic, and come in different "flavors", such as spherical and elongated particle shapes for steric repulsion, pusher and puller flow fields for hydrodynamics, etc. The combination of the various aspects is expected to lead to new emergent behavior. However, it is a priori not evident whether shape and hydrodynamics act synergistically or antagonistically to generate motility-induced clustering (MIC) and phase separation (MIPS). We employ a model of prolate spheroidal microswimmers-called squirmers-in quasi-two-dimensional confinement to address this issue by mesoscale hydrodynamic simulations. For comparison, non-hydrodynamic active Brownian particles (ABPs) are considered to elucidate the contribution of hydrodynamic interactions on MIC and MIPS. For spherical particles, the comparison between ABP and hydrodynamic-squirmer ensembles reveals a suppression of MIPS due to hydrodynamic interactions. Yet, our analysis shows that dynamic clusters exist, with a broad size distribution. The fundamental difference between ABPs and squirmers is attributed to an increased reorientation of squirmers by hydrodynamic torques during their collisions. In contrast, for elongated squirmers, hydrodynamics interactions enhance MIPS. The transition to a phase-separated state strongly depends on the nature of the swimmer's flow field -with an increased tendency toward MIPS for pullers, a reduced tendency for pushers. Thus, hydrodynamic interactions show opposing effects on MIPS for spherical and elongated microswimmers. Our results imply that details of the propulsion mechanism of biological microswimmers, like pattern and time dependence of the flagellar beat, may be very important to determine their collective behavior. arXiv:1807.01211v1 [cond-mat.soft]

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Section: Collective Behavior Of Squirmers-brief Summary Of Previomentioning

confidence: 91%

Clustering of microswimmers: interplay of shape and hydrodynamics

et al. 2018

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“…As we show in Appendix C, using Eqs. (18) and (19) ensures that, in general, the rate of work done by the particles on the fluid is correctly balanced by the viscous dissipation. These definitions also ensure that the stresslets do no work on the fluid.…”

Section: Fluctuating Fcmmentioning

confidence: 99%

“…If periodic or no-slip conditions are imposed on the bounding surfaces, integration by parts of Eqs. (18) and (19) reveals that the particle angular velocities and local rates-ofstrain reduce to the standard FCM definitions for these quantities which are the local volume averages of the fluid vorticity and rate-of-strain, respectively. With this in mind, the constraint Eq.…”

Section: Fluctuating Fcmmentioning

confidence: 99%

Simulating Brownian suspensions with fluctuating hydrodynamics

Delmotte

Keaveny

2015

The Journal of Chemical Physics

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Fluctuating hydrodynamics has been successfully combined with several computational methods to rapidly compute the correlated random velocities of Brownian particles. In the overdamped limit where both particle and fluid inertia are ignored, one must also account for a Brownian drift term in order to successfully update the particle positions. In this paper, we present an efficient computational method for the dynamic simulation of Brownian suspensions with fluctuating hydrodynamics that handles both computations and provides a similar approximation as Stokesian Dynamics for dilute and semidilute suspensions. This advancement relies on combining the fluctuating force-coupling method (FCM) with a new midpoint time-integration scheme we refer to as the drifter-corrector (DC). The DC resolves the drift term for fluctuating hydrodynamics-based methods at a minimal computational cost when constraints are imposed on the fluid flow to obtain the stresslet corrections to the particle hydrodynamic interactions. With the DC, this constraint need only be imposed once per time step, reducing the simulation cost to nearly that of a completely deterministic simulation. By performing a series of simulations, we show that the DC with fluctuating FCM is an effective and versatile approach as it reproduces both the equilibrium distribution and the evolution of particulate suspensions in periodic as well as bounded domains.In addition, we demonstrate that fluctuating FCM coupled with the DC provides an efficient and accurate method for large-scale dynamic simulation of colloidal dispersions and the study of processes such as colloidal gelation.

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“…Theoretical and numerical studies have investigated various aspects of active suspensions at different scales, from single particle dynamics to suspension rheology. While discrete-particle simulations that incorporate long-ranged hydrodynamic effects can capture observed large-scale features of these systems [9][10][11][12][13], constructing accurate continuum models is essential to their characterization and analysis, and for making new predictions of macroscale behaviors [2].…”

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confidence: 99%

Analytical structure, dynamics, and coarse graining of a kinetic model of an active fluid

Gao¹,

Betterton²,

Jhang³

et al. 2017

Phys. Rev. Fluids

100

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We analyze one of the simplest active suspensions with complex dynamics: a suspension of immotile "Extensor" particles that exert active extensile dipolar stresses on the fluid in which they are immersed. This is relevant to several experimental systems, such as recently studied tripartite rods that create extensile flows by consuming a chemical fuel. We first describe the system through a Doi-Onsager kinetic theory based on microscopic modeling. This theory captures the active stresses produced by the particles that can drive hydrodynamic instabilities, as well as the steric interactions of rod-like particles that lead to nematic alignment. This active nematic system yields complex flows and disclination defect dynamics very similar to phenomenological Landau-deGennes Q-tensor theories for active nematic fluids, as well as by more complex Doi-Onsager theories for polar microtubule/motor-protein systems. We apply the quasi-equilibrium Bingham closure, used to study suspensions of passive microscopic rods, to develop a non-standard Q-tensor theory. We demonstrate through simulation that this "BQ-tensor" theory gives an excellent analytical and statistical accounting of the suspension's complex dynamics, at a far reduced computational cost. Finally, we apply the BQ-tensor model to study the dynamics of Extensor suspensions in circular and biconcave domains. In circular domains, we reproduce previous results for systems with weak nematic alignment, but for strong alignment find novel dynamics with activity-controlled defect production and absorption at the boundaries of the domain. In bi-concave domains, a Fredericks-like transition occurs as the width of the neck connecting the two disks is varied.

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Large-scale simulation of steady and time-dependent active suspensions with the force-coupling method

Cited by 43 publications

References 77 publications

Clustering of microswimmers: interplay of shape and hydrodynamics

Clustering of microswimmers: interplay of shape and hydrodynamics

Simulating Brownian suspensions with fluctuating hydrodynamics

Analytical structure, dynamics, and coarse graining of a kinetic model of an active fluid

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