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DY: Fachverband Dynamik und Statistische Physik

DY 38: Microswimmers (joint session DY/CPP)

DY 38.5: Vortrag

Mittwoch, 3. April 2019, 16:30–16:45, H19

Microswimmers in an axisymmetric vortex flow: from Hamiltonian dynamics to clustering — •José-Agustín Arguedas-Leiva and Michael Wilczek — Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany

Microswimmers appear in a wide variety of settings, ranging from phytoplankton in the ocean to bacteria in laboratory flows, and are known to give rise to many physically interesting phenomena. One such phenomenon is the clustering of otherwise neutrally buoyant particles. Its occurrence, and in particular the importance of physical parameters such as particle shape and swimming velocity, are currently not fully understood.

Here, we study the the distribution and clustering of swimmers in a two-dimensional axisymmetric vortex flow. Due to its simplicity, this system allows for a number of insights: We find that spherical swimmers follow phase-space preserving Hamiltonian dynamics, excluding the possibibility for clustering. Interestingly, changing the particles’ shape breaks the Hamiltonian structure of the dynamics, and clustering can occur. Based on this observation we identify a single control parameter: an effective swimming velocity, which takes into account both the particles’ shape and velocity. By characterizing the topology of the underlying phase space our results help to clarify the role of motility and shape-dependent hydrodynamic interactions.