Active turbulence in microswimmer suspensions -- the role of active hydrodynamic stress and volume exclusion
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| Main Authors: | , , , |
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| Format: | Preprint |
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2021
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| _version_ | 1866913371496906752 |
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| author | Qi, Kai Westphal, Elmar Gompper, Gerhard Winkler, Roland G. |
| author_facet | Qi, Kai Westphal, Elmar Gompper, Gerhard Winkler, Roland G. |
| contents | Microswimmers exhibit an intriguing, highly-dynamic collective motion with large-scale swirling and streaming patterns, denoted as active turbulence -- reminiscent of classical high-Reynolds-number hydrodynamic turbulence. Various experimental, numerical, and theoretical approaches have been applied to elucidate similarities and differences to inertial hydrodynamic and active turbulence. These studies reveal a wide spectrum of possible structural and dynamical behaviors of active mesoscale systems, not necessarily consistent with the predictions of the Kolmogorov-Kraichnan theory of turbulence. We use squirmers embedded in a mesoscale fluid, modeled by the multiparticle collision dynamics (MPC) approach, to explore the collective behavior of bacteria-type microswimmers. Our model includes the active hydrodynamic stress generated by propulsion, and a rotlet dipole characteristic for flagellated bacteria. We find emergent clusters, activity-induced phase separation, and swarming, depending on density, active stress, and the rotlet dipole strength. The analysis of the squirmer dynamics in the swarming phase yields Kolomogorov-Kraichnan-type hydrodynamic turbulence and energy spectra for sufficiently high concentrations and strong rotlet dipoles. This emphasizes the paramount importance of the hydrodynamic flow field for swarming and bacterial turbulence. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2108_09566 |
| institution | arXiv |
| publishDate | 2021 |
| record_format | arxiv |
| spellingShingle | Active turbulence in microswimmer suspensions -- the role of active hydrodynamic stress and volume exclusion Qi, Kai Westphal, Elmar Gompper, Gerhard Winkler, Roland G. Soft Condensed Matter Biological Physics Microswimmers exhibit an intriguing, highly-dynamic collective motion with large-scale swirling and streaming patterns, denoted as active turbulence -- reminiscent of classical high-Reynolds-number hydrodynamic turbulence. Various experimental, numerical, and theoretical approaches have been applied to elucidate similarities and differences to inertial hydrodynamic and active turbulence. These studies reveal a wide spectrum of possible structural and dynamical behaviors of active mesoscale systems, not necessarily consistent with the predictions of the Kolmogorov-Kraichnan theory of turbulence. We use squirmers embedded in a mesoscale fluid, modeled by the multiparticle collision dynamics (MPC) approach, to explore the collective behavior of bacteria-type microswimmers. Our model includes the active hydrodynamic stress generated by propulsion, and a rotlet dipole characteristic for flagellated bacteria. We find emergent clusters, activity-induced phase separation, and swarming, depending on density, active stress, and the rotlet dipole strength. The analysis of the squirmer dynamics in the swarming phase yields Kolomogorov-Kraichnan-type hydrodynamic turbulence and energy spectra for sufficiently high concentrations and strong rotlet dipoles. This emphasizes the paramount importance of the hydrodynamic flow field for swarming and bacterial turbulence. |
| title | Active turbulence in microswimmer suspensions -- the role of active hydrodynamic stress and volume exclusion |
| topic | Soft Condensed Matter Biological Physics |
| url | https://arxiv.org/abs/2108.09566 |