Berlin 2018 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 30: Modeling and Simulation of Soft Matter I (joint session CPP/DY)

DY 30.1: Hauptvortrag

Dienstag, 13. März 2018, 14:00–14:30, PC 203

The role of correlations in the collective behaviour of microswimmer suspensions — •Alexander Morozov — University of Edinburgh, Edinburgh, UK

Recent years witnessed a significant interest in physical, biological and engineering properties of self-propelled particles, such as bacteria or synthetic microswimmers. The main distinction of this ’active matter’ from its passive counterpart is the ability to extract energy from the environment (consume food) and convert it into directed motion. One of the most striking consequences of this distinction is the appearance of collective motion in self-propelled particles suspended in a fluid observed in recent experiments and simulations: at low densities particles move around in an uncorrelated fashion, while at higher densities they organise into jets and vortices comprising many individual swimmers. Although this problem recieved significant attention in recent years, the precise origin of the transition is poorly understood.

In this talk I will present a numerical method based on a Lattice-Boltzmann algorithm to simulate hydrodynamic interactions between a large number of model swimmers (order 10⁵), represented by extended force dipoles. Using this method we simulate dilute suspensions of self-propelled particles and show that, even below the transition, swimmers move in a correlated fashion that cannot be described by a mean-field approach. We develop a novel kinetic theory that captures these correlations and is non-perturbative in the swimmer density, and reveals the asymmetry between pusher and puller swimmers below the transition to turbulence.