Inverse centrifugal effect induced by collective motion of vortices in rotating turbulent convection

TL;DR

This study reveals an unexpected outward collective motion of vortices in rotating turbulent convection, driven by symmetry-breaking and vortex interactions, challenging traditional centrifugal expectations.

Contribution

It demonstrates the existence of anomalous vortex motion and collective behavior in rotating turbulence, supported by experimental and numerical evidence.

Findings

Vortices exhibit outward motion under rapid rotation.

Vortex clusters show scale-free velocity correlations.

Long-range correlations lead to collective vortex motion.

Abstract

When a fluid system is subject to strong rotation, centrifugal fluid motion is expected, i.e., denser (lighter) fluid moves outward (inward) from (toward) the axis of rotation. Here we demonstrate, both experimentally and numerically, the existence of an unexpected outward motion of warm and lighter vortices in rotating turbulent convection. This anomalous vortex motion occurs under rapid rotations when the centrifugal buoyancy is sufficiently strong to induce a symmetry-breaking in the vorticity field, i.e., the vorticity of the cold anticyclones overrides that of the warm cyclones. We show that through hydrodynamic interactions the densely populated vortices can self-aggregate into coherent clusters and exhibit collective motion in this flow regime. Interestingly, the correlation of the vortex velocity fluctuations within a cluster is scale-free, with the correlation length being about 30% of the cluster length. Such long-range correlation leads to the collective outward motion of cyclones. Our study provides new understanding of vortex dynamics that are widely present in nature.