We extensively study the Toner-Tu-Swift-Hohenberg model of motile active matter by means of direct numerical simulations in a two-dimensional confined domain. By exploring the space of parameters of the model we investigate the emergence of a new state of active turbulence which occurs when the aligning interactions and the self-propulsion of the swimmers are strong. This regime of flocking turbulence is characterized by a population of few strong vortices, each surrounded by an island of coherent flocking motion. The energy spectrum of flocking turbulence displays a power-law scaling with an exponent which depends weakly on the model parameters. By increasing the confinement we observe that the system, after a long transient characterized by power-law-distributed transition times, switches to the ordered state of a single giant vortex.
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http://dx.doi.org/10.1103/PhysRevE.107.055107 | DOI Listing |
Phys Rev Lett
May 2024
Department of Materials Science and Physical Chemistry, Universitat de Barcelona, 08028 Barcelona, Spain.
We investigate experimentally the dynamic phase transition of a two-dimensional active nematic layer interfaced with a passive liquid crystal. Under a temperature ramp that leads to the transition of the passive liquid into a highly anisotropic lamellar smectic-A phase, and in the presence of a magnetic field, the coupled active nematic reorganizes its flow and orientational patterns from the turbulent into a quasilaminar regime aligned perpendicularly to the field. Remarkably, while the phase transition of the passive fluid is known to be continuous, or second order, our observations reveal intermittent dynamics of the order parameter and the coexistence of aligned and turbulent regions in the active nematic, a signature of discontinuous, or first order, phase transitions, similar to what is known to occur in relation to flocking in dry active matter.
View Article and Find Full Text PDFPLoS Biol
June 2024
University of North Carolina at Chapel Hill, Department of Biology, Chapel Hill, North Carolina, United States of America.
Much has been written about the energetic effects of animals moving in schools or flocks, but experimental results are few and often ambiguous. A new study in PLOS Biology shows that schooling greatly reduces the cost of transport for fish in turbulent flow.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
October 2023
Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637.
From flocks of birds to biomolecular assemblies, systems in which many individual components independently consume energy to perform mechanical work exhibit a wide array of striking behaviors. Methods to quantify the dynamics of these so-called active systems generally aim to extract important length or time scales from experimental fields. Because such methods focus on extracting scalar values, they do not wring maximal information from experimental data.
View Article and Find Full Text PDFPhys Rev E
May 2023
Dipartimento di Fisica and INFN, Università degli Studi di Torino, via P. Giuria 1, 10125 Torino, Italy.
We extensively study the Toner-Tu-Swift-Hohenberg model of motile active matter by means of direct numerical simulations in a two-dimensional confined domain. By exploring the space of parameters of the model we investigate the emergence of a new state of active turbulence which occurs when the aligning interactions and the self-propulsion of the swimmers are strong. This regime of flocking turbulence is characterized by a population of few strong vortices, each surrounded by an island of coherent flocking motion.
View Article and Find Full Text PDFNat Commun
April 2022
Department of Physics and Astronomy, School of Natural Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
From the motion of fish and birds, to migrating herds of ungulates, collective motion has attracted people for centuries. Active soft matter exhibits a plethora of emergent dynamic behaviors that mimic those of biological systems. Here we introduce an active system composed of dynamic dissipative solitons, i.
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