Collective Flows Drive Cavitation in Spinner Monolayers

TL;DR

This paper investigates how hydrodynamic interactions in spinner monolayers lead to cavitation phenomena, revealing an instability driven by collective flows that can be controlled or suppressed by boundary conditions and particle concentration.

Contribution

It demonstrates the emergence of cavitation due to collective hydrodynamic flows in spinner monolayers and explores how confinement and concentration influence this instability.

Findings

Instability causes particle voids and fluid vortices.

Hydrodynamic lift forces drive cavitation.

Confinement suppresses cavitation, while reduced concentration induces oscillations.

Abstract

Hydrodynamic interactions can give rise to a collective motion of rotating particles. This, in turn, can lead to coherent fluid flows. Using large scale hydrodynamic simulations, we study the coupling between these two in spinner monolayers at weakly inertial regime. We observe an instability, where the initially uniform particle layer separates into particle void and particle rich areas. The particle void region corresponds to a fluid vortex, and it is driven by a surrounding spinner edge current. We show that the instability originates from a hydrodynamic lift force between the particle and fluid flows. The cavitation can be tuned by the strength of the collective flows. It is suppressed when the spinners are confined by a no-slip surface, and multiple cavity and oscillating cavity states are observed when the particle concentration is reduced.