Berlin 2018 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 31: Microswimmers DY II (joint session DY/CPP/BP)
BP 31.3: Vortrag
Donnerstag, 15. März 2018, 10:30–10:45, BH-N 243
Mesoscale turbulence in active suspensions subjected to orienting external fields — •Henning Reinken1, Sebastian Heidenreich2, Markus Bär2, and Sabine H. L. Klapp1 — 1Institut für Theoretische Physik, Technische Universität Berlin, Berlin, Germany — 2Mathematische Modellierung und Datenanalyse, Physikalisch-Technische Bundesanstalt, Berlin, Germany
Active fluids show a variety of self-sustained non-equilibrium phenomena. An intriguing example is the emergence of a turbulent state in bacterial suspensions, denoted as mesoscale turbulence [1]. Recent publications have shown that a fourth order field theory for the collective microswimmer velocity describes the main features of mesoscale turbulence, including the emergence of a typical vortex size [2,3]. This theory couples the polar order parameter of the microswimmers to the solvent velocity and can be derived from a microscopic Langevin model including hydrodynamic and steric interactions via the Fokker-Planck equation [3,4]. In this work, we extend the theory towards the impact of orienting external fields (e.g. for magnetotactic bacteria or gravitactic algae cells). Using linear stability analysis and weakly nonlinear analysis, we investigate the influence of such external fields on the emerging structures. In addition, we verify our results via numerical solution of the equations.
[1] M. Marchetti et al., Rev. Mod. Phys. 85, 1143 (2013).
[2] J. Dunkel et al., New J. Phys. 15, 045016 (2013).
[3] S. Heidenreich et al., Phys. Rev. E 94, 020601(R) (2016).
[4] H. Reinken et al., in preparation.