Routes to Chaotic Flow in Active Suspensions

PhD defence by Robin Vincent Bölsterli

Assessment Committee

Associate Professor Ala Trusina, Niels Bohr Institute, University of Copenhagen (Chairperson)
Professor Karsten Kruse, University of Geneva
Professor Andreas Menzel, University Magdeburg

Supervisors

Assistant Professor Amin Doostmohammadi
Associate Professor Ala Trusina

Department

Niels Bohr Institute

Place

Building: C, Room: Aud. A, Blegdamsvej 17, 2300 Copenhagen

Email address to gain access to the thesis: robin.boelsterli@gmail.com.
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Short description of the thesis

Dense suspensions of self-propelled units spontaneously develop chaotic flows of vortices and jets. This thesis examines three separate aspects of that transition. In an idealised active nematic, an information-theoretic mixing measure is used to locate an activity threshold, at which the defect path length and the velocity correlation length also peak. In a channel, periodic contraction of the wall is shown to activate chaotic flow in a suspension that would otherwise remain quiescent, with topological defects nucleating only above a threshold contraction amplitude. Finally, a particle-resolved model, in which the flow around every swimmer is solved explicitly, maps how the flow generated by individual swimmers shapes the collective state.