Self-organized patterns in active turbulence and ensembles of active particles

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• Michael Wilczek (Universität Bayreuth)
• Friday 14 June 2024, 14:00-14:50
• Seminar Room 1, Newton Institute.

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ADIW04 - Anti-Diffusion in Multiphase and Active Flows

In this talk, I am going to review some of our recent works on large-scale patterns in active fluids. In the first part, we will consider a simple model for polar active fluids which is well-known for exhibiting active turbulence [1]. Using large-scale computations we show that also self-organized vortex crystals can emerge after a turbulent transient [2,3], similar to recent observations in two-dimensional forced Navier-Stokes turbulence [4].The second part of the talk focuses on active nematic turbulence [5]. We show that in certain parameter ranges for the active and elastic properties of the fluid the usual Stokes approximation breaks down and large-scale flow patterns can emerge due to an inverse transport of energy to large scales [6].In the final part of the presentation, I will take a more microscopic perspective and present ongoing work on disk-like active Brownian particles in which the geometric centers do not coincide with the centers of mass. This property leads to torques even for simple steric interaction, which can significantly affect large-scale aggregation phenomena in this model. [1] Wensink, Dunkel, Heidenreich, Drescher, Goldstein, Löwen, Yeomans. Meso-scale turbulence in living fluids, PNAS 109 , 14308 (2012)[2] James, Bos, Wilczek, Turbulence and turbulent pattern formation in a minimal model for active fluids, Phys. Rev. Fluids 3, 061101® (2018)[3] James, Suchla, Dunkel, Wilczek, Emergence and melting of active vortex crystals, Nat. Commun. 12, 5630 (2021)[4] van Kan, Favier, Julien, Knobloch, From a vortex gas to a vortex crystal in instability-driven two-dimensional turbulence, J. Fluid Mech. 984, A41 (2024)[5] Giomi, Geometry and topology of turbulence in active nematics Physical Review X 5 , 031003 (2015)[6] Koch & Wilczek, Role of Advective Inertia in Active Nematic Turbulence, PRL 127 , 268005 (2021)

This talk is part of the Isaac Newton Institute Seminar Series series.

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