Regensburg 2025 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
DY: Fachverband Dynamik und Statistische Physik
DY 14: Focus Session: Nonlinear Dynamics in Biological Systems I (joint session DY/BP)
DY 14.3: Talk
Tuesday, March 18, 2025, 10:15–10:30, H43
Pattern selection and the route to turbulence in polar active fluids — Henning Reinken1, Sebastian Heidenreich2, •Markus Bär2, 3, and Sabine Klapp3 — 1OVGU Magdeburg, Germany — 2Physikalisch-Technische Bundesanstalt, Germany — 3TU Berlin, Germany
Active fluids, such as suspensions of microswimmers, are well known to self-organize into complex spatio-temporal flow patterns. An intriguing example is mesoscale turbulence, a state of dynamic vortex structures exhibiting a characteristic length scale. Here, we employ a minimal model for the effective microswimmer velocity field to explore how the turbulent state develops from regular, stationary vortex patterns when activity is increased. First, we demonstrate analytically that the system develops a stationary square vortex lattice in the absence of nonlinear advection. Subsequently, we perform an extended stability analysis and uncover a linear instability, above which the square vortex lattice becomes unstable. In numerical simulations, we confirm that this instability is predictive for the unset of turbulence. In addition, an extended region of hysteresis where turbulence and a stable vortex lattice coexist, is found Reference: H. Reinken, S. Heidenreich, M. Bär, S. Klapp, New J. Phys. 26 063026 (2024).
Keywords: Active Fluids; Nonlinear Dynamics; Active Turbulence; Pattern Formation