Jump Rope Vortex in Liquid Metal Convection

TL;DR

This paper reveals a novel three-dimensional 'jump rope vortex' mode in turbulent liquid metal convection, observed through combined experiments, which significantly advances understanding of large scale circulations in natural and industrial systems.

Contribution

It introduces the jump rope vortex as a new large-scale flow mode in turbulent convection, observed in liquid gallium and other viscous fluids, expanding the understanding of flow dynamics.

Findings

The jump rope vortex is a dominant 3D mode in turbulent convection.

This mode exists in both liquid gallium and more viscous fluids like water.

The jump rope vortex influences large-scale circulation patterns in natural systems.

Abstract

Understanding large scale circulations (LSCs) in turbulent convective systems is important for the study of stars, planets and in many industrial applications. The canonical model of the LSC is quasi-planar with additional horizontal sloshing and torsional modes [Brown E, Ahlers G (2009) J. Fluid Mech. 638:383--400; Funfschilling D, Ahlers G (2004) Phys. Rev. Lett. 92(19):194502; Xi HD et al. (2009) Phys. Rev. Lett. 102(4):044503; Zhou Q et al. (2009) J. Fluid Mech. 630:367--390]. Using liquid gallium as the working fluid, we show via coupled laboratory-numerical experiments that the LSC in a tank with aspect ratios greater than unity takes instead the form of a "jump rope vortex", a strongly three-dimensional mode that periodically orbits around the tank following a motion much like a jump rope on a playground. Further experiments show that this jump rope flow also exists in more viscous fluids such as water, albeit with a far smaller signal. Thus, this new jump rope mode is an essential component of the turbulent convection that underlies our observations of natural systems.