Flow transitions and length scales of a channel-confined active nematic

Samui, Abhik; Yeomans, Julia M.; Thampi, Sumesh P.

doi:10.1039/d1sm01434j

Cited by 15 publications

(21 citation statements)

References 54 publications

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“…In two-dimensions, the general trend [25,26] is that confining geometries much smaller than L α result in stationary systems while systems much larger than L α result in chaotic flows or mesoscale turbulence. Between these extremes, systems exhibit a variety of geometrydependent dynamical states, such as coherent flows accompanied by either stationary or nontrivial periodic dynamics of the director field.…”

Section: Introductionmentioning

confidence: 99%

Exact Coherent Structures and Phase Space Geometry of Preturbulent 2D Active Nematic Channel Flow

et al. 2022

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This work is a unified study of stable and unstable steady states of 2D active nematic channel flow using the framework of Exact Coherent Structures (ECS). ECS are stationary, periodic, quasiperiodic, or traveling wave solutions of the governing equations that, together with their invariant manifolds, organize the dynamics of nonlinear continuum systems. We extend our earlier work on ECS in the preturbulent regime by performing a comprehensive study of stable and unstable ECS for a wide range of activity values spanning the preturbulent and turbulent regimes.In the weakly turbulent regime, we compute more than 200 unstable ECS that co-exist at a single set of parameters, and uncover the role of symmetries in organizing the phase space geometry. We provide conclusive numerical evidence that in the preturbulent regime, generic trajectories shadow a series of unstable ECS before settling onto an attractor. Finally, our studies hint at shadowing of quasiperiodic type ECS in the turbulent regime.

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Section: Introductionmentioning

confidence: 99%

Exact Coherent Structures and Phase Space Geometry of Preturbulent 2D Active Nematic Channel Flow

et al. 2022

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“…Polar active fluids, such as dense suspensions of swimming bacteria, transition from laminar to undulating and periodic travelling flows upon increasing the channel width, eventually giving place to turbulent dynamics [21][22][23][24]. In active nematics, both numerical studies [25][26][27][28] and experiments with microtubule-kinesin suspensions [29] with strong anchoring to the channel walls have revealed a transition from laminar to oscillatory flows to a lattice of counter-rotating flow vortices with associated order of disclinations in the nematic texture. Similar flow states and transitions are also reported in other geometries, such as in circular confinement [15,19,30].…”

Section: Introductionmentioning

confidence: 99%

Boundaries control active channel flows

Gulati

Shankar

2022

Front. Phys.

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Boundary conditions dictate how fluids, including liquid crystals, flow when pumped through a channel. Can boundary conditions also be used to control internally driven active fluids that generate flows spontaneously? By using numerical simulations and stability analysis we explore how parallel surface anchoring of active agents at the boundaries and substrate drag can be used to rectify coherent flow of an active polar fluid in a 2D channel. Upon increasing activity, a succession of dynamical states is obtained, from laminar flow to vortex arrays to eventual turbulence, that are controlled by the interplay between the hydrodynamic screening length and the extrapolation length quantifying the anchoring strength of the orientational order parameter. We highlight the key role of symmetry in both flow and order and show that coherent laminar flow with net throughput is only possible for weak anchoring and intermediate activity. Our work demonstrates the possibility of controlling the nature and properties of active flows in a channel simply by patterning the confining boundaries.

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Section: Introductionmentioning

confidence: 99%

Boundaries control active channel flows

Gulati,

Shankar,

Marchetti

2022

Preprint

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Flow transitions and length scales of a channel-confined active nematic

Abstract: Different flow regimes realised by a channel-confined active nematic have a characteristic length same as channel width. Flow structures exhibit the intrinsic length scale of the fluid only in the fully developed active turbulence regime.

Cited by 15 publications

References 54 publications

Exact Coherent Structures and Phase Space Geometry of Preturbulent 2D Active Nematic Channel Flow

Exact Coherent Structures and Phase Space Geometry of Preturbulent 2D Active Nematic Channel Flow

Boundaries control active channel flows

Boundaries control active channel flows

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