Saturday, 15 July 2017

Swirling swarms of bacteria offer insights on turbulence

When bacteria swim at just the right speed, swirling vortices emerge. As those patterns disintegrate into chaos, physicists detect a telling mathematical signature.

In physical systems, turbulence emerges when the smooth flow of a liquid or gas is disrupted, producing unpredictable swirls like those in billowing smoke, foaming surf, and a stomach-dropping flight. Try as they might, scientists still cannot predict precisely how smoke, water, air, or any other substance will move about during turbulence.

Something similar appears to happen within certain biological systems. Recently, scientists have discovered a turbulence-like dynamic emerging from what they call active fluids, such as a dense mass of swimming bacteria or a collection of movement-generating proteins suspended in liquid. Unlike a drop of water, these active fluids move on their own power. The biological turbulence they generate therefore differs in some significant ways from the physical phenomenon, and the relationship between these two types of turbulence remains controversial and poorly understood.

The discovery bridges the two by showing that as it emerges and propagates, turbulence follows the same pattern in masses of swimming bacteria as it does in air, water, or any other physical system.


Amin Doostmohammadi, Tyler N. Shendruk, Kristian Thijssen, Julia M. Yeomans. Onset of meso-scale turbulence in active nematics. Nature Communications, 2017; 8: 15326 DOI: 10.1038/NCOMMS15326

Posted by Dr. Tim Sandle