Defect turbulence in a dense suspension of polar, active swimmers

Fuente: arXiv
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Autori principali: Rana, Navdeep, Chatterjee, Rayan, Ro, Sunghan, Levine, Dov, Ramaswamy, Sriram, Perlekar, Prasad
Natura: Preprint
Pubblicazione: 2023
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author Rana, Navdeep
Chatterjee, Rayan
Ro, Sunghan
Levine, Dov
Ramaswamy, Sriram
Perlekar, Prasad
author_facet Rana, Navdeep
Chatterjee, Rayan
Ro, Sunghan
Levine, Dov
Ramaswamy, Sriram
Perlekar, Prasad
contents We study the effects of inertia in dense suspensions of polar swimmers. The hydrodynamic velocity field and the polar order parameter field describe the dynamics of the suspension. We show that a dimensionless parameter $R$ (ratio of the swimmer self-advection speed to the active stress invasion speed) controls the stability of an ordered swimmer suspension. For $R$ smaller than a threshold $R_1$, perturbations grow at a rate proportional to their wave number $q$. Beyond $R_1$, we show that the growth rate is $\mathcal{O}(q^2)$ until a second threshold $R=R_2$ is reached. The suspension is stable for $R>R_2$. We perform direct numerical simulations to investigate the steady state properties and observe defect turbulence for $R<R_2$. An investigation of the spatial organisation of defects unravels a hidden transition: for small $R\approx 0$ defects are uniformly distributed and cluster as $R\to R_1$. Beyond $R_1$, clustering saturates and defects are arranged in nearly string-like structures.
format Preprint
id arxiv_https___arxiv_org_abs_2305_15197
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Defect turbulence in a dense suspension of polar, active swimmers
Rana, Navdeep
Chatterjee, Rayan
Ro, Sunghan
Levine, Dov
Ramaswamy, Sriram
Perlekar, Prasad
Soft Condensed Matter
Fluid Dynamics
We study the effects of inertia in dense suspensions of polar swimmers. The hydrodynamic velocity field and the polar order parameter field describe the dynamics of the suspension. We show that a dimensionless parameter $R$ (ratio of the swimmer self-advection speed to the active stress invasion speed) controls the stability of an ordered swimmer suspension. For $R$ smaller than a threshold $R_1$, perturbations grow at a rate proportional to their wave number $q$. Beyond $R_1$, we show that the growth rate is $\mathcal{O}(q^2)$ until a second threshold $R=R_2$ is reached. The suspension is stable for $R>R_2$. We perform direct numerical simulations to investigate the steady state properties and observe defect turbulence for $R<R_2$. An investigation of the spatial organisation of defects unravels a hidden transition: for small $R\approx 0$ defects are uniformly distributed and cluster as $R\to R_1$. Beyond $R_1$, clustering saturates and defects are arranged in nearly string-like structures.
title Defect turbulence in a dense suspension of polar, active swimmers
topic Soft Condensed Matter
Fluid Dynamics
url https://arxiv.org/abs/2305.15197