Dynamic mode structure of active turbulence

Henshaw, Richard J.; Martin, Olivia G.; Guasto, Jeffrey S.

doi:10.1103/physrevfluids.8.023101

Cited by 5 publications

(2 citation statements)

References 69 publications

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“…It would also be interesting to compare the ECS discovered in the current work to dynamic modes obtained in active turbulence using data-driven dynamical systems approaches such as Proper Orthogonal Decomposition and Dynamic Mode Decomposition [33]. Finally, detection of stable and unstable ECS in an experimentally realizable active nematic system such as the 2D annulus [24,27,90] will be considered.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…From an engineering perspective, there is substantial interest in understanding how to navigate the large space of spatiotemporal structures in confined active nematics [28][29][30][31][32], by spatial, or spatiotemporal modulation of activity. There are also fundamental unanswered questions related to active turbulence in confinement [26,33]: how confined active fluids become turbulent, how to characterize them, and how to promote or inhibit turbulence. Some recent theoretical and computational studies have derived coarse-grained statistical descriptions [6,[34][35][36][37] of active turbulence, focusing on energy spectra and spatial organization of statistically steady states, rather than deterministic dynamics.…”

Section: Introductionmentioning

confidence: 99%

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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: Discussion and Concluding Remarksmentioning

confidence: 99%

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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Cascades and Kolmogorov's lognormal scaling in two-dimensional bacterial turbulence

Huang

2024

Physics of Fluids

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Collective movements of bacteria exhibit a remarkable pattern of turbulence-like vortices, in which the Richardson cascade plays an important role. In this work, we examine the energy and enstrophy cascades and their associated lognormal statistics using experimental velocity field data. The coherent structure observed on a large scale is due to the presence of the inverse energy cascade, while the kinetic energy is dissipated at all scales, since these active movements occur below the fluid viscosity scale. The forward enstrophy cascade occurs with injection at all scales and may be represented by other nonlinear interactions that are not captured by the existing experimental data. Furthermore, the lognormal statistics for both energy dissipation and enstrophy fields is verified in accordance with the Kolmogorov 1962 refined theory of turbulence. Their scaling exponents can be well described by the lognormal formula with intermittency parameters comparable with those of the three-dimensional hydrodynamic turbulence. The joint analysis of the multifractal measures of the energy dissipation rate and enstrophy follows an ellipse model from the lognormal statistics. Our results confirm the coexistence of the inverse energy cascade and the intermittency correction of the velocity scaling in this active fluid system. An inverse energy cascade diagram below the fluid viscosity is summarized to describe the observed two-dimensional bacterial turbulence. Our work provides an example of an active-flow model benchmark.

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Exploring regular and turbulent flow states in active nematic channel flow via Exact Coherent Structures and their invariant manifolds

Wagner,

Pallock,

Park

et al. 2023

Phys. Rev. Fluids

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Dynamic mode structure of active turbulence

Cited by 5 publications

References 69 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

Cascades and Kolmogorov's lognormal scaling in two-dimensional bacterial turbulence

Exploring regular and turbulent flow states in active nematic channel flow via Exact Coherent Structures and their invariant manifolds

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