Diffusion properties of self-propelled particles in cellular flows

Caprini, Lorenzo; Cecconi, Fabio; Puglisi, Andrea; Sarracino, Alessandro

doi:10.1039/d0sm00450b

Cited by 14 publications

(9 citation statements)

References 78 publications

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“…To predict the shape of D L (a), we resort to an argument similar to that already used in ref. 90, where the long-timediffusion has been predicted for an active particle advected in a two-dimensional laminar flow. At first, we calculate the effective persistence length c of the active particle.…”

Section: Long Time-diffusion Coefficientmentioning

confidence: 99%

Dynamics of active particles with space-dependent swim velocity

et al. 2022

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Section: Long Time-diffusion Coefficientmentioning

confidence: 99%

Dynamics of active particles with space-dependent swim velocity

et al. 2022

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“…the inability of two ants to occupy the same space) [32]. Regardless, the prevailing behaviour is that of super-diffusivity [37,38]. Super-diffusivity is not inherent to SPPs; rather, it is generally indicative of field or current-induced drift [38][39][40].…”

Section: Treadmillingmentioning

confidence: 99%

Treadmilling and dynamic protrusions in fire ant rafts

Wagner

Such

Hobbs

et al. 2021

J. R. Soc. Interface.

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Fire ants ( Solenopsis invicta ) are exemplary for their formation of cohered, buoyant and dynamic structures composed entirely of their own bodies when exposed to flooded environments. Here, we observe tether-like protrusions that emerge from aggregated fire ant rafts when docked to stationary, vertical rods. Ant rafts comprise a floating, structural network of interconnected ants on which a layer of freely active ants walk. We show here that sustained shape evolution is permitted by the competing mechanisms of perpetual raft contraction aided by the transition of bulk structural ants to the free active layer and outward raft expansion owing to the deposition of free ants into the structural network at the edges, culminating in global treadmilling. Furthermore, we see that protrusions emerge as a result of asymmetries in the edge deposition rate of free ants. Employing both experimental characterization and a model for self-propelled particles in strong confinement, we interpret that these asymmetries are likely to occur stochastically owing to wall accumulation effects and directional motion of active ants when strongly confined by the protrusions' relatively narrow boundaries. Together, these effects may realize the cooperative, yet spontaneous formation of protrusions that fire ants sometimes use for functional exploration and to escape flooded environments.

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“…To predict the shape of D L (α), we resort to an argument similar to that already used in Ref. [87], where the long-time-diffusion has been predicted for an active particle advected in a two-dimensional laminar flow. At first, we calculate the effective persistence length of the active particle.…”

Section: Long Time-diffusion Coefficientmentioning

confidence: 99%

Dynamics of active particles with space-dependent swim velocity

Caprini,

Marconi,

Wittmann

et al. 2021

Preprint

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We study the dynamical properties of an active particle subject to a swimming speed explicitly depending on the particle position. The oscillating spatial profile of the swim velocity considered in this paper takes inspiration from experimental studies based on Janus particles whose speed can be modulated by an external source of light. We suggest and apply an appropriate model of an active Ornstein Uhlenbeck particle (AOUP) to the present case. This allows us to predict the stationary properties, by finding the exact solution of the steady-state probability distribution of particle position and velocity. From this, we obtain the spatial density profile and show that its form is consistent with the one found in the framework of other popular models. The reduced velocity distribution highlights the emergence of non-Gaussianity in our generalized AOUP model which becomes more evident as the spatial dependence of the velocity profile becomes more pronounced. Then, we focus on the time-dependent properties of the system. Velocity autocorrelation functions are studied in the steady-state combining numerical and analytical methods derived under suitable approximations. We observe a non-monotonic decay in the temporal shape of the velocity autocorrelation function which depends on the ratio between the persistence length and the spatial period of the swim velocity. Finally, we numerically and analytically study the mean square displacement and the long-time diffusion coefficient. The ballistic regime, observed in the small-time region, is deeply affected by the properties of the swim velocity landscape which induces also a crossover to a sub-ballistic but superdiffusive regime for intermediate times. Finally, the long-time diffusion coefficient decreases as the amplitude of the swim velocity oscillations increases because the diffusion is mainly determined by those regions where the particles are slow.

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Diffusion properties of self-propelled particles in cellular flows

Abstract: We study the dynamics of a self-propelled particle advected by a steady laminar flow unveiling its diffusive properties due to the interplay between the active force and the convective flow.

Cited by 14 publications

References 78 publications

Dynamics of active particles with space-dependent swim velocity

Dynamics of active particles with space-dependent swim velocity

Treadmilling and dynamic protrusions in fire ant rafts

Dynamics of active particles with space-dependent swim velocity

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