Flow reversals in turbulent convection via vortex reconnections

TL;DR

This paper investigates flow reversals in 2D turbulent convection, revealing that vortex reconnections of corner rolls cause flow restructuring and heat transport fluctuations, with reversals occurring within specific Rayleigh and Prandtl number ranges.

Contribution

The study provides a detailed numerical analysis of the vortex reconnection mechanism driving flow reversals in turbulent convection, highlighting flow configuration changes and parameter restrictions.

Findings

Flow reversals occur via vortex reconnection of corner rolls.

Flow restructuring causes large heat transport fluctuations.

Reversals happen within specific Rayleigh and Prandtl number ranges.

Abstract

We employ detailed numerical simulations to probe the mechanism of flow reversals in two-dimensional turbulent convection. We show that the reversals occur via vortex reconnection of two attracting corner rolls having same sign of vorticity, thus leading to major restructuring of the flow. Large fluctuations in heat transport are observed during the reversal due to this flow reconfiguration. The flow configurations during the reversals have been analyzed quantitatively using large-scale modes. Using these tools, we also show why flow reversals occur for a restricted range of Rayleigh and Prandt numbers.