Event

Inertial active suspensions: Stability and Turbulence

Title of the event	Inertial active suspensions: Stability and Turbulence
Series	LMP Seminar
Organizer	Physik lebender Materie
Speaker	Dr. Navdeep Rana
Speaker institution	Dept. of Living Matter Physics, MPI for Dynamics and Self-Organization, Göttingen
Type of event	Seminar
Category	Forschung
Registration required	Nein
Details	Suspensions of self-propelled particles, for example, bacteria, show spectacular collective behaviour. The Reynolds number, which measures the relative strength of inertial and viscous forces, characterizes such suspensions. In the low Reynolds number limit, where viscosity dominates over inertia, a uniform aligned state of swimmers is unstable to small perturbations. This instability lies at the heart of widely observed active turbulence. In this seminar, I will talk about swimmer suspensions at Reynolds number of order unity, where viscous and inertial forces are comparable. I will show how the dimensionless number R, a combination of suspension inertia, swimmer motility, and active stress, determines the stability of orientational order against small perturbations in extensile suspensions. At small R, perturbations grow at a rate linear to the magnitude of their wavevector, q. The growth is slower for an intermediate range of R, with a rate proportional to q². Finally, at large R, the flock becomes stable. Direct numerical simulations reveal that Malthusian suspensions show a transition from isotropic hedgehog-defect turbulence to phase turbulence as we increase R. On the other hand, Dense suspensions show a transition from vortex-defect turbulence to complete orientational order.
Date	Start: 08.02.2022, 14:00 Uhr Ende: 08.02.2022 , 15:30 Uhr
Location	Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS) (Am Faßberg 17) Video conference at www.zoom.us Meeting ID: 997 1155 2453 Passcode: 771001
Contact	Prof. Dr. Ramin Golestanian golestanian-office@ds.mpg.de