Streaks to Rings to Vortex Grids: Generic Patterns in Transient Convective Spin-Up

TL;DR

This paper investigates the transient formation of ringed patterns during the spin-up of evaporating fluids, revealing how force balances lead to vortex grid formation with potential implications for astrophysics and geophysics.

Contribution

It demonstrates the transient balance of Coriolis and viscous forces causes ringed patterns, linking them to vortex grid formation and turbulence in rotating convection.

Findings

Ringed patterns form during spin-up due to force balance.

Breakdown of rings leads to Kelvin-Helmholtz instability.

Vortex grid spacing scales with initial ring wavelength.

Abstract

We observe the transient formation of a ringed pattern state during spin-up of an evaporating fluid on a time scale of order a few Ekman spin-up times. The ringed state is probed using infrared thermometry and particle image velocimetry and it is demonstrated to be a consequence of the transient balance between Coriolis and viscous forces which dominate inertia, each of which are extracted from the measured velocity field. The breakdown of the ringed state is quantified in terms of the antiphasing of these force components which drives a Kelvin-Helmholtz instability and we show that the resulting vortex grid spacing scales with the ring wavelength. This is the fundamental route to quasi-two dimensional turbulent vortex flow and thus may have implications in astrophysics and geophysics wherein rotating convection is ubiquitous. sics.