Giant vortex dynamics in confined bacterial turbulence

Area of Science:

• Physics of complex systems
• Microbiology and biophysics
• Fluid dynamics

Background:

• Dense bacterial suspensions exhibit complex emergent behaviors.
• Turbulence in active matter systems, like bacteria, is a key area of research.
• Confined geometries can significantly alter self-organization patterns.

Purpose of the Study:

• To investigate the emergence of new states in bacterial turbulence within confined domains.
• To characterize the self-organization process leading to ordered structures.
• To compare numerical findings with potential experimental realizations.

Main Methods:

• Extensive numerical simulations using the Toner-Tu-Swift-Hohenberg model.
• Modeling dense bacterial suspensions in circular geometries.
• Analysis of flow patterns, angular momentum symmetry, and velocity profiles.

Main Results:

• Discovery of a stable, ordered state characterized by a single, giant vortex spanning the domain.
• Observation of broken angular momentum symmetry within the vortex.
• Identification of radial vorticity streaks in an annular region near the boundary.
• Radial velocity profile of the vortex aligns with analytical predictions.

Conclusions:

• Bacterial turbulence can self-organize into large-scale ordered structures in confined environments.
• The giant vortex state represents a novel phase of bacterial active matter.
• Provides parameters for designing future experiments to observe this phenomenon.