Collective Flows Drive Cavitation in Spinner Monolayers.

Area of Science:

• Fluid dynamics
• Soft matter physics
• Non-equilibrium systems

Background:

• Hydrodynamic interactions can induce collective motion in rotating particles.
• This collective motion can lead to the emergence of coherent fluid flows.
• Understanding the interplay between particle dynamics and fluid behavior is crucial in various physical systems.

Purpose of the Study:

• To investigate the coupling between collective particle motion and fluid flow in spinner monolayers.
• To identify and characterize instabilities arising from hydrodynamic interactions.
• To explore the role of hydrodynamic lift forces in particle-fluid coupling.

Main Methods:

• Large-scale hydrodynamic simulations were employed.
• The study focused on spinner monolayers in a weakly inertial regime.
• Analysis involved examining particle distribution, fluid flow patterns, and forces.

Main Results:

• An instability was observed, leading to the separation of the spinner layer into particle-rich and particle-void regions.
• The particle-void regions were identified as fluid vortices driven by spinner edge currents.
• Hydrodynamic lift forces were shown to be the origin of this instability, termed cavitation.
• Cavitation dynamics were tunable by collective flow strength and particle concentration.

Conclusions:

• Hydrodynamic lift forces drive instabilities in spinner monolayers, leading to vortex formation.
• The observed cavitation phenomenon is sensitive to confinement, collective flow strength, and particle concentration.
• This work provides insights into self-organization and pattern formation in active matter systems.