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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

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Published on: December 4, 2017

Meso-scale turbulence in living fluids.

Henricus H Wensink¹, Jörn Dunkel, Sebastian Heidenreich

¹Institute for Theoretical Physics II: Soft Matter, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany.

Proceedings of the National Academy of Sciences of the United States of America

|August 22, 2012

Summary

Researchers studied self-sustained turbulence in bacterial suspensions using experiments and simulations. They developed a minimal continuum model to describe active turbulence in biological systems.

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The Diffusion of Passive Tracers in Laminar Shear Flow

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Published on: May 1, 2018

Area of Science:

Physics
Fluid Dynamics
Biophysics

Background:

Turbulence is common in nature, but understanding it in active nonequilibrium fluids like microbial suspensions is challenging.
The collective dynamics of microorganisms create self-sustained turbulence, impacting microscale fluid mixing and transport.
Current models struggle to capture the universal or system-specific features of turbulence in living matter.

Purpose of the Study:

To identify statistical properties of self-sustained meso-scale turbulence in active biological systems.
To investigate the influence of dimensionality and boundary conditions on bacterial collective dynamics.
To propose a minimal continuum model for active turbulence in bacterial flows.

Main Methods:

Experiments involving dense Bacillus subtilis suspensions in quasi-2D and 3D geometries.
Particle simulations using a minimal model for self-propelled rods.
Development and numerical analysis of a minimal continuum model for incompressible bacterial flow.

Main Results:

Experimental results for bacterial flow statistics align with predictions from the self-propelled rod model.
High concentrations of bacteria show collective motion dominated by short-range interactions.
The proposed 2D continuum model successfully reproduces key features of experimentally observed active turbulence.

Conclusions:

The collective motion in dense bacterial suspensions can be modeled effectively using simplified frameworks.
A minimal continuum theory provides a basis for understanding and predicting active turbulence in biological systems.
This work advances the characterization of turbulence in active matter and its implications for microscale transport.