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Main Title: Multi-particle collision dynamics with a non-ideal equation of state. II. Collective dynamics of elongated squirmer rods
Author(s): Zantop, Arne W.
Stark, Holger
Type: Article
Abstract: Simulations of flow fields around microscopic objects typically require methods that both solve the Navier–Stokes equations and also include thermal fluctuations. One such method popular in the field of soft-matter physics is the particle-based simulation method of multi-particle collision dynamics (MPCD). However, in contrast to the typically incompressible real fluid, the fluid of the traditional MPCD methods obeys the ideal-gas equation of state. This can be problematic because most fluid properties strongly depend on the fluid density. In a recent article, we proposed an extended MPCD algorithm and derived its non-ideal equation of state and an expression for the viscosity. In the present work, we demonstrate its accuracy and efficiency for the simulations of the flow fields of single squirmers and of the collective dynamics of squirmer rods. We use two exemplary squirmer-rod systems for which we compare the outcome of the extended MPCD method to the well-established MPCD version with an Andersen thermostat. First, we explicitly demonstrate the reduced compressibility of the MPCD fluid in a cluster of squirmer rods. Second, for shorter rods, we show the interesting result that in simulations with the extended MPCD method, dynamic swarms are more pronounced and have a higher polar order. Finally, we present a thorough study of the state diagram of squirmer rods moving in the center plane of a Hele-Shaw geometry. From a small to large aspect ratio and density, we observe a disordered state, dynamic swarms, a single swarm, and a jammed cluster, which we characterize accordingly.
Subject(s): collision dynamics
elongated squirmer rods
flow fields
Navier–Stokes equations
thermal fluctuations
Issue Date: 6-Oct-2021
Date Available: 12-Nov-2021
Language Code: en
DDC Class: 530 Physik
Sponsor/Funder: DFG, 163436311, SFB 910: Kontrolle selbstorganisierender nichtlinearer Systeme: Theoretische Methoden und Anwendungskonzepte
Journal Title: The Journal of Chemical Physics
Publisher: American Institute of Physics
Volume: 155
Article Number: 134904
Publisher DOI: 10.1063/5.0064558
EISSN: 1089-7690
ISSN: 0021-9606
TU Affiliation(s): Fak. 2 Mathematik und Naturwissenschaften » Inst. Theoretische Physik » FG Statistische Physik weicher Materie und biologischer Systeme
Appears in Collections:Technische Universität Berlin » Publications

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