Turbulence-induced clustering in compressible active fluids.

Area of Science:

• Active matter physics
• Fluid dynamics
• Soft condensed matter

Background:

• Active polar fluids exhibit complex behaviors driven by self-propelled agents.
• Turbulence and emergent structures like clusters are key phenomena in these systems.

Purpose of the Study:

• To investigate a novel phase of active polar fluids characterized by dynamic cluster formation.
• To understand the mechanisms driving cluster creation and destruction in turbulent active fluids.

Main Methods:

• Development and analysis of a continuum model for compressible polar active fluids.
• Incorporation of experimental observations, including non-monotone speed-density relationships.

Main Results:

• Identification of a turbulent phase with continuous creation and destruction of dense clusters.
• Demonstration that cluster size is governed by characteristic vortex size.
• Modeling the interplay between self-advection and defect topology in driving this phase.

Conclusions:

• The novel phase arises from the interplay of self-advection and defect topology.
• Vortex size is a critical determinant of emergent cluster scales in active polar fluids.
• The continuum model captures key aspects of bacterial suspension dynamics.